Genetics: The Science of Heredity

Chapter 47th Grade Science

Mendel’s Work

• ______________ - “Father of Genetics”– A priest that conducted experiments in his garden

that revolutionized the study of heredity.– ___________ - the passing of physical

characteristics from parents to offspring– Mendel used pea plants to observe _________ of

pea plants.– _________ - a characteristic that an organism can

pass on to its offspring through its genes.

Gregor Mendel

Heredity

traits

traits

Mendel and Heredity

• Mendel experimented with hundreds of pea plants to understand the process of ________.

• ________ - the scientific study of heredity.• Mendel “crossed” pea plants with contrasting

________ and observed the outcomes of traits in the offspring.

• Mendel started his experiments with ________ pea plants or plants that have had the same trait for many generations.

heredity

Genetics

traits

purebred

Crossing Pea Plants

• __________ short pea plants come always come from short parent plants.Purebred

Mendel’s Experiments

Generations and Offspring

• _____________ - parent generation• _________________ - the offspring from the first

parent generation. “Filia” comes from the Latin word meaning son or daughter. This generation is noted as __ - all of the plants in this generation were tall.

• _________ - Mendel allowed the plants in the f₁ generation to self pollinate. The plants in the f₂ generation - the result was a mix of short and tall plants

P generation

First “filial” generation

f₁

F₂ generation

Mendel’s Conclusion

• Mendel’s Conclusions included:– Individual factors or sets of _________

information controls the __________ of traits in peas.• The factors that control each trait exist in _____ - one

from the _______ parent and one from the _______parent.• One factor in each pair can mask or hide the other

factor.

geneticinheritance

pairsfemale

male

Dominant and Recessive

• ________- factors that control a trait.• _____ - different forms of the gene• Offspring inherit one _______ from each parent – one

could be tall and the other could be short, both could be tall, both could be short – it depends on the ________ information from the parent.

• ____________ - the trait that always shows up in the organism when the allele is present

• ____________ - hidden whenever the dominant allele is present

Dominant allele

AllelesAllele

genetic

Gene

Recessive Allele

Genetics of Pea Plants

Alleles in Mendel’s Crosses

• ___________ - only pea plants that inherit two recessive alleles for short stems will be short.

• _________ - organism has two different alleles for a trait.

• ________ alleles mask the ________ alleles.• A dominant allele is represented by a ______

letter. Recessive alleles are represented by ________ letters.

Purebred short

hybrid

Dominant recessive

capital

Lower case

Pea Plant traits

Probability and Heredity

• ________ - a number that describes how likely it is that an event will occur. Not necessarily what will occur.

• Example: coin toss – the more tosses you make, the closer the actual results will be to the results predicted by probability.

• Each toss yields a result that is __________ of all other tosses.

probability

independent

Probability and Genetics

• Mendel was the first scientist to recognize that the principles of __________ can be used to predict the results of ___________.

• ____________ - a chart that shows all the possible combinations of ________ that can result from a genetic cross.

• The boxes in the Punnett Square represent the possible alleles that the offspring can _______.

probabilityGenetic crosses

Punnett Squarealleles

inherit

Punnett Square Examples

Phenotypes and Genotypes

• ____________ - an organisms physical appearance or visible traits.

• ___________ - an organisms genetic makeup, or allele combinations.

• ___________ - two identical alleles for a trait• ___________ - two different alleles for a trait• Mendel used the term _________ to describe

__________ pea plants.

phenotype

genotype

homozygous

heterozygous

hybridheterozygous

Codominance

• __________ - the alleles are neither dominant nor recessive – both alleles are expressed in the offspring.

Codominance

Chromosomes and Inheritance

• _______________________ - genes are carried from parents to their offspring on chromosomes.

• _______ - the process by which the number of chromosomes is reduced by half to form sex cells – ____________.– Chromosome pairs separate and are distributed to

two different cells.– The resulting sex cells have only half as many

chromosomes as the other cells in the organism.

Chromosome Theory of inheritance

meiosis

Sperm and egg

Meiosis

Meiosis and Punnett Square

• _____________-show the events that occur in meiosis.– When the _______________ separate and go into

two different ________, so do the _________ carried on each chromosome.

– Punnett Squares show the possible allele combinations after __________.

Punnett Square

Chromosome pairsSex cells allele

fertilization

Punnet Square

Genes

• The body cells of humans contain ____ chromosome pairs.

• Chromosomes are made up of many ______ joined together like beads on a string.

• Body cells contain between _______________• Each ______ controls a _____• The _______ are lined up in the same order

on each ___________.

23

genes

20,000-25,000 genes

gene trait

geneschromosome

Chromosomes and Genes

The DNA Connection

• _______ - control the production of ________ in an organisms cells.

• __________ - determine the size, shape, color and many other traits of an organisms.

• A gene is a section of _______ molecule that contains the information to code for a specific __________.

• Each _______ is located in a place on a _________

gene proteins

proteins

DNA

protein

genechromosome

Order of Bases

• _________contains the _____ that determines the structure of the ______.

• ___________ form a ___________ that specifies what type of ______ will be produced.

• _________ - long chains molecules of individual __________.

• A group of _____________ codes for one specific __________.

gene codeprotein

Nitrogen Bases Genetic codeprotein

proteinsAmino acids

3 DNA basesAmino acid

How cells make proteins

• ___________ - production of proteins – cells use the information from a gene on a chromosome to produce a specific _______.

• Protein synthesis takes place on the ________ in the __________ of the cell.

• ____ - ribonucleuc acid – “Messenger” carries the genetic code from the DNA inside of the nucleus to the ________.

Protein Synthesis

protein

ribosome

cytoplasm

RNA

cytoplasm

DNA / RNA

• DNA has ________, RNA has _________• Both DNA and RNA contain ___________ but

they are different• DNA has four bases - ___________• RNA has ____________• 2 types of RNA - ____________ and

____________

2 strands 1 strand

Sugar molecules

A, T, C, G

A, C, G and uracil

Messenger RNA

Transfer RNA

RNA

• ____________ - copies the coded message from the DNA in the nucleus and carries the message to the ribosome in the cytoplasm.

• ____________ - carries amino acids to the ribosomes and adds them to the growing protein

Messenger RNA

Transfer RNA

Translating the Code

• 1. Message transferred to the messenger RNA• 2. Messenger RNA attaches to the Ribosome• 3. Transfer RNA attaches to the Messenger

RNA• 4. Protein Production continues.• www.brainpop.com• Page 134-135

Mutations

• _________ - any change in a gene or chromosome.

• Mutations can cause a cell to produce an incorrect protein during ____________ - this change can effect the organisms trait or phenotype.

• Mutations that occur in sex cells can be passed on to _______. Other mutations are not passed on.

Mutation

Protein synthesis

offspring