mendenlian genetics heredity and traits. bellringer- remediation questions copy question in green...
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Mendenlian GeneticsHeredity and traits
Bellringer- Remediation
questionsCopy Question in GREEN
and correct answer choice
2 minutes per slide
1. Which of the following accurately states the difference between plant and animal cells?
A. Animal cells have stomata that allow for gas exchange
B. Plant cells have chloroplasts that are sites of chemical reactions
C. Plant cells have stromal cells that make up connective tissue
D. Animal cells have chloropplasts that turn glucose into ATP
2. If you examined a cell under a microscope and found it had a
nucleus and other organelles, how would you classify it?
A. It is a plant cell
B. It is an animal cell
C. It is a eukaryotic cell
D. It is a prokaryotic cell
3. Bacterial are prokaryotic cells, while multicellular and more sophisticated single-celled
organisms are eukaryotic. Which of these describes a prokaryotic cell
and NOT a eukaryotic cell? A. Sunlight is absorbed by chloroplasts in
the cell
B. Molecules join together to assemble a permeable cell membrane
C. The nuclear membrane dissassembles and chromosomes align in a cell
D. DNA is distributed loosely within the cell rather than in chromosomes
4. Because of the function of most plant leaves is to carry out
photosynthesis, their cells contain many more of what organelle than
any other part of the plant?A. Chloroplasts
B. Mitochondria
C. Nuclei
D. vacuoles
5. Which statement is true for both prokaryotes and
eukaryotes?
A. They can only reproduce asexually
B. Their DNA is found within a nucleus
C. Their DNA is found within the mitochondria
D. Their DNA is replicated during reproduction
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Gregor Mendel(1822-1884)
Responsible for the Laws governing Inheritance of Traits
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Gregor Johann MendelAustrian monk
Studied the inheritance of traits in pea plants
Developed the laws of inheritance
Law of segregationLaw of independent assortmentLaw of dominance
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Gregor Johann MendelBetween 1856 and 1863, Mendel cultivated and tested some 28,000 pea plants
He found that the plants' offspring retained traits of the parents
Called the “Father of Genetics"
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Genetic Terminology Trait - any characteristic
that can be passed from parent to offspring
Heredity - passing of traits from parent to offspring
Genetics - study of genes & heredity
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Mendel Chose Pea plants to test his theories
Pea plants expressed different traits (i.e) green or yellow seed
Genes are factors that are passed on to offspring to parents Genes are found on DNA
Alleles are different forms of a gene 2 alleles = a Gene
Alleles: alternative versions of a gene.
The gene for a particular inherited character resides at a specific locus (position) on homologous chromosome.
For each character, an organism inherits two alleles, one from each parent
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Applying the Law of Segregation
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Principle of Dominance
In simple mendelian genetics, alleles can be either dominant or recessive
Dominant alleles: expresses the trait it represents; masks over recessive traits Represented by a capital letter (ex. R)
Recessive alleles: only is expressed when it is not paired with the dominant allele Represented by a lower-case letter (ex. r)
Hybrid (heterozygous) Gene: a gene with both a dominant and recessive allele Ex. Rr
Homozygous genes: have the same trait for both alleles Ex. (RR) or (rr)
bb
WW or Ww
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More Terminology
Genotype - gene combination for a trait (e.g. RR, Rr, rr)
Phenotype - the physical feature resulting from a genotype (e.g. red, white) i.e.- what you see
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Example: Eye color
-Genotype: bb
-Phenotype: Blue
color
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Eight Pea Plant Traits Seed shape --- Round (R) or Wrinkled (r)
Seed Color ---- Yellow (Y) or Green (y)
Pod Shape --- Smooth (S) or wrinkled (s)
Pod Color --- Green (G) or Yellow (g)
Seed Coat Color ---Gray (G) or White (g)
Flower position---Axial (A) or Terminal (a)
Plant Height --- Tall (T) or Short (t)
Flower color --- Purple (P) or white (p)
Principle of Segregation
If Maternal genotype (mom) has Bb and Paternal genotype (dad) has BB, how does the offspring end up with Bb? Or BB?
During the formation of gametes (meiosis) the alleles will separate or segregate into different gametes
Bb
B
bB
B
Traits are passed down from generation to
generation
P generation (parental generation)
F1 generation (first filial generation, the word filial from the Latin word for "son") are the hybrid offspring.
Allowing these F1 hybrids to self-pollinate produces:
F2 generation (second filial generation).
It is the analysis of this that lead to an understanding of genetic crosses.
Probability and Punnett Squares
Punnett square: diagram showing the probabilities of the possible outcomes of a genetic cross
Punnett squares - probability diagram illustrating the possible offspring of a mating.
Ss X Ss
gametes
A Testcross is designed to reveal whether an organism that displays the dominant phenotype is homozygous or heterozygous.
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Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Wrinkled seeds
RR x rr
P1 Monohybrid Cross
R
R
rr
Rr
RrRr
Rr
Genotype: Rr
Phenotype: Round
GenotypicRatio: All alike
PhenotypicRatio: All alike
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P1 Monohybrid Cross Review
Homozygous dominant x Homozygous recessive
ALL Offspring Heterozygous (hybrids) and thus round
Offspring called F1 generation
Genotypic & Phenotypic ratio is ALL ALIKE
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Trait: Seed Shape
Alleles: R – Round r – Wrinkled
Cross: Round seeds x Round seeds
F1 Monohybrid Cross
R
r
rR
RR
rrRr
RrG.Ratio: 1:2:1
P.Ratio: 3:1
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Cross 2 heterozygous round seeds
Welcome Back!
Get Ready for your remediation bellringer!
1. Over time, the climate of an island became drier, which resulted in changes to
the populations of various island finch species. Finch populations with a certain
beak shape thrived, while those not having that beak shape decreased. Which of the following describes a necessary condition for these changes in the finch populations
to occur? A. fewer mutations
B. limited food resources
C. limited beak variations
D. overproduction of offspring
2. Which of these would have the least effect on natural selection in a
subspecies of giraffes that is geographically isolated from other
subspecies of giraffes?
A. available niches
B. existing predators
C. chromosome number
D. available food resources
3. Mutations within a DNA sequence are
A. natural processes that produce genetic diversity
B. natural processes that always affect the phenotype
C. unnatural processes that always affect the phenotype
D. unnatural processes that are harmful to genetic diversity
4. Which of the following best illustrates natural selection?
A. An organism with favorable genetic variations will tend to survive and breed successfully.
B. A population monopolizes all of the resources in its habitat, forcing other species to migrate.
C. A community whose members work together utilizing all existing resources and migratory routes.
D. The largest organisms in a species receive the only breeding opportunities.
5. In his book On the Origin of the Species, Charles Darwin described how species change over time. Which of the
following is NOT part of his observations that describes the mechanisms of natural
selection?
A. Organisms produce more offspring than can survive.
B. Disease and natural disaster will limit population growth.
C. Species today descended with modifications from ancestral species.
D. Organisms with advantages will survive and reproduce.
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Summary of Mendel’s laws
LAWPARENT CROSS
OFFSPRING
DOMINANCE TT x tt tall x short
100% Tt tall
SEGREGATIONTt x Tt tall x tall
75% tall 25% short
INDEPENDENT ASSORTMENT
RrGg x RrGg round & green x round & green
9/16 round seeds & green pods 3/16 round seeds & yellow pods 3/16 wrinkled seeds & green pods 1/16 wrinkled seeds & yellow podscopyright cmassengale
Law of Independent assortment and Dihybrid
crosses Genes for a different trait can segregate independently during gamete formation
Dihybrid CrossExample: pea COLOR and Texture can be cross together
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Dihybrid Cross A breeding experiment that tracks
the inheritance of two traits.
Mendel’s “Law of Independent Assortment”
a. Each pair of alleles segregates independently during gamete formation
b. Formula: 2n (n = # of heterozygotes)
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Question:How many gametes will be
produced for the following allele arrangements?
Remember: 2n (n = # of heterozygotes)
1. RrYy
2. AaBbCCDd
3. MmNnOoPPQQRrssTtQq
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Answer:1. RrYy: 2n = 22 = 4 gametes
RY Ry rY ry
2. AaBbCCDd: 2n = 23 = 8 gametesABCD ABCd AbCD AbCdaBCD aBCd abCD abCD
3. MmNnOoPPQQRrssTtQq: 2n = 26 = 64 gametes
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Dihybrid Cross Traits: Seed shape & Seed color
Alleles: R round r wrinkled Y yellow y green
RrYy x RrYy
RY Ry rY ry RY Ry rY ry
All possible gamete combinationscopyright cmassengale
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Dihybrid Cross
RY Ry rY ry
RY
Ry
rY
ry
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Dihybrid Cross
RRYY
RRYy
RrYY
RrYy
RRYy
RRyy
RrYy
Rryy
RrYY
RrYy
rrYY
rrYy
RrYy
Rryy
rrYy
rryy
Round/Yellow: 9
Round/green: 3
wrinkled/Yellow: 3
wrinkled/green: 1
9:3:3:1 phenotypic ratio
RY Ry rY ry
RY
Ry
rY
ry
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We Do: Dihybrid Practice Problems
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Incomplete Dominanceand
Codominance
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Incomplete Dominance
Some traits are neither dominant nor recessive
So what happens to the Hybrid? (Rr)
Incomplete Dominance results in an intermediate phenotype for the hybrid species
Example:
RR-WHITE rr- RED Rr- PINK
Co-Dominance (multiple alleles)
Some traits are both, in a sense, dominant
Therefor, the hybrid of the two traits will result in both traits being expressed
Example:
BB- White
bb-Brown
Bb- brown and white
Roan Cow
Blood Type and Co-dominance
Another example of a co-dominant trait is blood type
Blood type A and B are both dominant (O is recessive) AA- homozygous type A BB homozygous type B AB- type AB AO- Type A BO- Type B OO- Type O
Hero Blood When receiving blood
transfusions, people must receive blood that matches their own blood types The body will reject a foreign
blood type
Because type O(-) is recessive, it can be given to any other blood type
Downside of being O(-): You can only receive O(-) Only 9% of the population is O(-)
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Sex-linked Traits
Traits (genes) located on the sex chromosomes
Sex chromosomes are X and Y XX genotype for females XY genotype for males
Many sex-linked traits carried on X chromosome
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Sex-linked Traits
Sex Chromosomes
XX chromosome - female Xy chromosome - male
fruit flyeye color
Example: Eye color in fruit flies
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There are NO ALLELES on the Y-chromosome
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Sex-linked Trait Problem Example: Eye color in fruit flies
(red-eyed male) x (white-eyed female) XRY x XrXr
Remember: the Y chromosome in males does not carry traits.
RR = red eyed
Rr = red eyed
rr = white eyed
XY = male
XX = female
XR
Xr Xr
Y
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Sex-linked Trait Solution:
XR Xr
Xr Y
XR Xr
Xr Y
50% red eyed female
50% white eyed male
XR
Xr Xr
Y
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Female Carriers
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Sex-linked trait facts
1. Y-chromosome carries NO traits
2. Male offspring always show the trait of their mother
3. Females can be carriers of the recessive trait herterozygotes
4. Males are never carriers They either have the trait or
the don’t
Polygenic Traits• Polygenic traits, or
continuous traits, are governed by alleles at two or more loci, • each locus has some
influence on the phenotype.
• Hair, eye and skin color, height, face shape are polygenic traits
• So, several genes influence the outcome of the trait
Environmental Influence on Gene
Expression For some traits, a particular
environment can influence the expression of the gene
Examples: Temperature and Light
Himalayan Rabbit fur color
Drugs and chemicals Cyclopean fish
Gender Baldness
You Do: Patterns of Inheritance Practice
Problems
Bellringer- Human Impact Remediation
1. New fuels are being produced by converting corn and grasses into
compounds containing alcohols that can be broken down for energy in
various engines. The purpose of this research is to
A. reduce the use of nonrenewable resources.
B. increase the rate of air pollution.
C. reduce the rate of homeostasis in organisms.
D. cause a loss of biodiversity in the rain forests.
2. The presence of wastes, such as plastic bags and motor oil, in lakes and
streams miles away from developed areas suggests that
A. ecosystems are interconnected and human action can alter ecosystem equilibrium.
B. recycling programs have failed to conserve biotic resources.
C. natural processes can alter ecosystem stability.
D. direct harvesting practices have led to irreversible destruction of ecosystems.
3. The northern elephant seal was almost hunted to extinction in the 1800s.
By the late 1890s, approximately one hundred seals were left, reducing the
gene pool of the population. What will be the consequence of this reduction?
A. Competition within the population will increase.
B. The surviving elephant seals will be better able to adapt.
C. Inbreeding will be less frequent among the remaining population.
D. The elephant seals will be more vulnerable to environmental change.
4. When fertilizers run off farmland into streams and ponds, the nitrogen content of the water increases. This can lead to rapid
growth of algae in a process called eutrophication. How can this process affect
other organisms in the water?
A. Oxygen is used up as algae is decomposed, reducing the amount available to other organisms.
B. The water becomes better able to support aerobic organisms.
C. The algae provide food for fishes and other organisms, leading to decreased algae populations.
D. The extra nitrogen provides additional food for the other organisms, increasing their population
What is a Pedigree?
A pedigree is a chart of the genetic history of family over several generations.
Scientists or a genetic counselor would find out about your family history and make this chart to analyze.
Pedigree Analysis
Goals of Pedigree Analysis
1. Determine the mode of inheritance: dominant, recessive, partial dominance, sex-linked, autosomal, mitochondrial, maternal effect.
2. Determine the probability of an affected offspring for a given cross.
Pedigree Symbols
• Half shaded shapes signify carriers (heterozygotes)
Interpreting a Pedigree Chart
1. Determine if the pedigree chart shows an autosomal or X-linked disease.
If most of the males in the pedigree are affected the disorder is X-linked
If it is a 50/50 ratio between men and women the disorder is autosomal.
Example of Pedigree Charts
Is it Autosomal or X-linked?
Answer: Autosomal
Interpreting a Pedigree Chart
2. Determine whether the disorder is dominant or recessive.
If the disorder is dominant, one of the parents must have the disorder.
If the disorder is recessive, neither parent has to have the disorder because they can be heterozygous.
Example of Pedigree Charts
Dominant or Recessive?
Answer: Dominant
Example of Pedigree Charts
Dominant or Recessive?
Answer: Recessive
Summary
Pedigrees are family trees that explain your genetic history.
Pedigrees are used to find out the probability of a child having a disorder in a particular family.
To begin to interpret a pedigree, determine if the disease or condition is autosomal or X-linked and dominant or recessive.
Pedigree Chart -Cystic Fibrosis