1. Biology Content Review Genetics
Gateway
Biology Content Review
Genetics

2. Meiosis
Sexual reproduction (Why is meiosis required for sexual reproduction?)
Form gametes (sperm and egg)
Daughter cells
Four produced (two nuclear divisions)
Haploid (n, cuts the number of chromosomes in half)
Different from parent and unique from each other

3. Meiosis Steps Prophase I Metaphase I Anaphase I Telophase I
Prophase II
Metaphase II
Anaphase II
Telophase II

4. Meiosis

5. Mitosis & Meiosis MITOSIS Produces _identical_ genetic copies
1 cell copies its DNA and organelles and then splits into_2_ cells
Occurs for the purposes of growth and repair or asexual reproduction
Happens in body cells
Consists of Prophase, Metaphase, Anaphase, Telophse
MEIOSIS
Produces _gametes___ or sex cells (sperm and egg) for sexual reproduction
1 cell copies its DNA and splits into __4_ cells during two cell divisions
Each of the resulting gametes is __different__ from the starting cell and from each other
The end cells have ½ the amount of DNA as the starting cell
Happens in cells of the testes and ovaries only
Consists of Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II,

6. Comparing Mitosis and Meiosis:

7. Comparing Mitosis and Meiosis:

8. Genetics/ DNA Its shape is a twisted ladder, or a double helix.
DNA is made up of sugars and phosphates (the side of the “ladder”) and pairs of nitrogen bases (the steps of the “ladder”). The bases in DNA are called adenine, thymine, guanine, and cytosine. _A__ always bonds with _T___ and ___G__ always bonds with _C___.

9. Genetics/ DNA Heredity and Mendelian Genetics
Genetics: The study of heredity (the passing of traits from parents to offspring)
Gregor Mendel: The father of genetics.
DNA: Consists of many genes
Gene: Stretch of DNA that codes for a given trait.
Allele: Alternate version of a gene

10. Genetics/ DNA Dominant and Recessive Traits Dominant Allele
Gene that is fully expressed.
Masks/ “speaks louder than” a recessive allele.
Recessive Allele
Masked/not expressed if dominant allele is present.
Only expressed if dominant allele is absent.

11. Genetics/ DNA Genotype The genetic makeup of an organism
Homozygous: having two of the same allele
Heterozygous: having two different alleles.
Homozygous Dominant: having two dominant alleles
Homozygous Recessive: having two recessive alleles
Heterozygous: having one of each allele

12. Genetics/ DNA Phenotype
The physical and physiological traits of an organism
How the genes are expressed
What you would see in a photograph

13. Example:
In peas, Y is a dominant allele that instructs for yellow seeds; y is a recessive allele that produces green seeds. Given the following genotypes, fill in the term that best describes each, and then indicate what the phenotype of the organism will be.

14. DNA/ Genetics
A Punnett Square can be used to predict the genotypes and phenotypes of the offspring produced by a given genetic cross.
Generations
Parental (P): The organisms involved in the initial cross
First Filial (F1): The offspring of the Parental Generation
Second Filial (F2): The offspring of the First Filial Generation

15. Example:
A chicken and a rooster mate. The chicken has white feathers and the rooster has brown feathers. Brown is dominant, and white is recessive. Assuming the rooster is heterozygous, predict the frequency of each genotype and phenotype in their offspring.
What is the cellular process that determines which alleles an offspring will receive from their parents? Meiosis

16. Practice:
1. A plant that is homozygous dominant for height is crossed with a plant that is homozygous recessive. (T = tall; t = short). Use a Punnett Square to predict the genotypic and phenotypic ratios of the F1 generation.

17. Practice:
2. Using question number 1, what would be the genotypic and phenotypic ratios of a cross of two F1 individuals?

18. DNA/ Genetics Determining Sex Human male: XY Human female: XX
Which parent determines the sex of a human offspring? Father
What is the probability of having a boy? A girl? 50%/50%

19. DNA/ Genetics Sex linked traits Carried on the X chromosome
Example: hemophilia, color blindness.
Disorders occur more often in males than females. Why? Males have one X chromosome, so if one is defective, they do not have a backup copy as do females.

20. DNA/ Genetics Mutation A change in the base sequence of DNA.
A change in DNA can lead to a change in the protein coded for by that gene.
A change in the protein structure can lead to certain disorders, for example, sickle cell anemia.

21. DNA
Genetics is the scientific study of ___heredity__, or the passing of traits from parents to offspring.
Traits are passed by means of _genes_, or deoxyribonucleic acid. DNA contains segments called __codons_ which code for certain __proteins___. These proteins control the traits of an organism.
More about DNA:
DNA makes up the _chromosomes___ that are found in the nucleus of a cell.
DNA is a type of nucleic acid.
Its shape is a twisted ladder, or a _double helix____.
DNA is made up of sugars and phosphates (the side of the “ladder”) and pairs of nitrogen bases (the steps of the “ladder”). The bases in DNA are called adenine, thymine, guanine, and cytosine. __A_ always bonds with _T__ and _C__ always bonds with _G__.
Any change in the base sequence of DNA is known as a _mutation____. Mutations can lead to a change in the protein that is coded for by the affected gene. This change can lead to certain disorders like sickle-cell anemia.

22. Genetics