genetics. 1. what is a chromosome? 2. where are chromosomes located? a threadlike structure of dna...
TRANSCRIPT
Genetics
1. What is a chromosome?
2. Where are chromosomes located?
A threadlike structure of DNA and protein that contains genetic information.
In eukaryotes chromosomes are found in the nucleus; in prokaryotes, they are found in the cytoplasm
Chromosomes
Genetics
3. What are genes?
4. Where are genes found?
Genetics
Special sequences of DNA that codes for a protein and thus determines a trait.
Genes are found on chromosomes.
5. What is genetics?
6. Who is considered the father of genetics?
Genetics
Genetics is the scientific study of heredity.
Gregor Mendel, an Austrian monk Mendel’s paper
on genetics 1865
7. What kind of organism did Mendel study?
8. What are some of the traits that Mendel studied?
Genetics
Mendel studied pea plants
Seed color and shape; Pod color and shape; Flower color and position
9. What is an allele?
Genetics
An allele is one of a number of different forms of a gene.
For example, the gene for flower color in peas has two alleles—purple (P) and white (p).
And the gene for seed pod color has two alleles—Green (G) and yellow (g).
Green Seed Pod
allele
Yellow Seed Pod
allele
Purple flower allele
White flower allele
10. What is meant by Mendelian Genetics?
Genetics
Any traits that are controlled by a single gene. For example, flower color is controlled by a single gene that has two alleles.
Locus for Flower Color
Gene
Locus for Pod Color
Gene
11. What is a locus?The specific location of a gene on a chromosome.
12. What is a true breeding plant?
Genetics
True breeding plants always make offspring identical to themselves. For example, white flower plants always produce white flower offspring.
Parents
Offspring
And purple flower plants always produce purple flower offspring.
Parents
Offspring
P P P P
Parents
Offspring
Alleles
14. How many alleles for a single gene can an organism have?
Genetics
Two. Offspring inherit one allele from the male parent and the other allele from the female parent.
13. What is the universal symbol for a male and female?
Male Female
P P P P
Click once for animation
15. State Mendel’s Principle of Dominance?
Genetics
This principle states that some alleles are dominant and others are recessive.
For example, a plant that has a purple allele (P) and a white allele (p) will have purple flowers. This is because the purple allele is dominant over the white allele.
pPRecessive
allele(white)
Dominant allele
(purple)
Dominant color
(purple)
17. Define phenotype?
Genetics
16. Define genotype?
The phenotype is the physical characteristic of an organism. For example, the phenotype of the flower shown at right is white.
The genotype is the genetic makeup of an organism. For example, the possible genotypes for a purple flower could be PP or Pp.
19. What is the phenotype of each flower?
Genetics
18. Identify the genotype for each flower shown below?
Pp PP ppPurple Purple White
Genotypes =
Phenotypes =
21. Which of the following is a hybrid?
Genetics
A hybrid is an organism that has two different alleles for a particular gene.
Pp
20. What is a hybrid?
PP pp
Hybrid plant True breeding plants
Genetics
Homo- means “same” and -zygous means “pair.”Homozygous refers to the fact that two alleles for a gene are the same. For example PP or pp
22. What does homozygous mean
Hetero- means “different. Heterozygous refers to the fact that two alleles for a gene are different. For example, Pp.
23. What does heterozygous mean
Pp
PP
pp
Genetics24. Match the flower genotypes on the left to the terms on the right.
Homozygous recessive
Heterozygous
Homozygous dominant
25. How do the alleles get from parents to offspring?
Genetics
The chromosomes the alleles reside on are packaged in gametes (sex cells), like egg and sperm. Egg Sperm
When egg and sperm meet, fertilization occurs, making a new cell called a zygote.
Fertilization
The zygote will divide by mitosis and develop into an embryo.
Embryo
Genetics
Pp x Pp
a. Since this is a monohybrid cross, you should have drawn a 2 x 2 Punnett square.
26. Draw a Punnett square for the following hybrid cross:
Genetics
b. Next, you should have written the parent genotypes above the Punnett square.
Pp x Pp
26. Draw a Punnett square for the following hybrid cross:
Genetics
c. Then you should have placed the sex symbols on the Punnett square.
26. Draw a Punnett square for the following hybrid cross:
Pp x Pp
Genetics
d. After the sex symbols, you were to determine the alleles for the sperm and eggs.
26. Draw a Punnett square for the following hybrid cross:
Pp x Pp
P p
p
P
Genetics
26. Draw a Punnett square for the following hybrid cross:
e. Finally, you should have combined the alleles of the gametes to form zygotes
Pp x Pp
P p
p
P PP
Pp
Pp
pp
Genetics
28. Draw ovals around those alleles found in sperm
Pp x Pp
P p
p
P
Pp
PpPP
pp29. Draw circles around those alleles found in eggs.
30. Draw diamonds around the alleles of the offspring.
27. Draw squares around the alleles of the parents
Punnett Square Review
Genetics
32. Put squares around the heterozygous offspring.
Pp x Pp
P p
p
P
Pp
PpPP
pp33. Draw a diamond around the homozygous recessive offspring.
31. Circle the homozygous dominant offspring.
Punnett Square Review
Genetics
35. Put diamonds around the hybrid offspring.
Pp x Pp
P p
p
P
Pp
PpPP
pp36. Why is this called a monohybrid cross?
34. Circle the purebred offspring.
Punnett Square Review
Mono- means “one.” Hybrid refers to having different alleles for the same gene. Since the cross deals with only one character (mono-) and each parent is a hybrid, the cross is described as monohybrid.
Genetics
38. What is the phenotypic ratio of the offspring?
Pp x Pp
P p
p
P
Pp
PpPP
pp
37. What is the genotypic ratio of the offspring?
Punnett Square Review
PP : Pp : pp 1 : 2 : 1
Purple : White 3 : 1
Genetics
39. State Mendel’s Principle of Segregation.
Allele pairs separate during gamete formation.
Meiosis
Germ cellGametes
Genetics
40. State Mendel’s Principle of Independent Assortment.
Allele pairs for different traits separate independently during gamete formation.
Germ cellGametes
Chromosome alignment A
Chromosome alignment B
orFour
different types of gametes
1
2
3
4
Genetics
41. Study the table below for a pattern. What number do you think goes in the last space? (Assume genes are on separate chromosomes and sort independently)
Genotype Possible number of unique gametes
Aa
AaBb
AaBbCc
AaBbCcDd
AaBbCcDdEe
2
4
8
16
1 gene
2 genes
3 genes
4 genes
5 genes 32
The formula for calculating the
number of possible gametes
is 2n, where 2 equals the number of
different alleles and n is the
number of genes.
Genetics
42. Humans have 23 sets of chromosomes. How many different ways could these chromosomes sort independently?
Hint: You would use the same formula as was done for alleles and genes (2n). However, this time
n represents the number of chromosome sets.
2n = 223 = 8,388,608 different combinations
Genetics
AaRr x AaRr
43. Draw a Punnett square for the following dihybrid cross:
Since this is a dihybrid cross, you should have drawn a 4 x 4 Punnett square. Each parent will also be able to produce 4 different kinds of gametes.
AR Ar aR ar
AR
Ar
aR
ar
AARR AARr AaRr AaRr
AARr AArr AaRr AArr
AaRR AaRr aaRR aaRr
AaRr Aarr aaRr aarr
Genetics
AaRr x AaRr
44. What is the genotypic frequency of this dihybrid cross?
AR Ar aR ar
AR
Ar
aR
ar
AARR AARr AaRr AaRr
AARr AArr AaRr AArr
AaRR AaRr aaRR aaRr
AaRr Aarr aaRr aarr
Genotype FrequencyAARRAARrAArrAaRRAaRrAarraaRRaaRraarr
1/162/162/161/165/161/161/162/161/16
Genetics
AaRr x AaRr
45. What is the phenotypic frequency of this dihybrid cross?
AR Ar aR ar
AR
Ar
aR
ar
AARR AARr AaRr AaRr
AARr AArr AaRr AArr
AaRR AaRr aaRR aaRr
AaRr Aarr aaRr aarr
Phenotype Frequency
Axial, Round
Axial, Wrinkled
Terminal, Round
Terminal, Wrinkled
9/16
3/16
3/16
1/16
A = Axial flowersA = Terminal flowers
R = Round seedsr = Wrinkled seeds