1. Sexual Reproduction
Chapter 10

2. Let’s Review!
The cell cycle is when a cell makes a copy of itself for:
Growth, Repair, Replacement
BODY (autosomal/somatic) cells reproduce by mitosis
some organisms do also, but we will talk about that later!

3. Chromosomes Homologous Chromosomes: chromosomes that make a pair
They have the same length, same centromere position, and control the same inherited trait

5. Gametes Gamete: Sex cell (sperm and egg)
Have half the # of chromosomes as compared to autosomal cells
Ensures that an organism has the same number of chromosomes from generation to generation
In humans, each gamete has 23 chromosomes
n = number of chromosomes in a gamete

6. Gametes Haploid: n Diploid: 2n (female n + male n)
When 2 human gametes combine through fertilization, 23 homologous chromosomes are formed
Meaning - Mom has 23 chromosomes, Dad has 23 chromosomes  You have 46 chromosomes

7. Meiosis
Process that creates gametes, occurs in reproductive structures
Cell reproduction that reduces the # of
chromosomes
Mitosis MAINTAINS the number of chromosomes in the cell
Meiosis REDUCES it by half by splitting homologous chromosomes
2n  n
Interphase, Meiosis I and II

8. Interphase
Replication of DNA
Protein synthesis

9. Meiosis I
Prophase I: Centrioles move to opposite poles, spindle fibers form and bind to sister chromatids at the centromere
Crossing Over (synapse): chromosome segments are exchanged between homologous chromosomes

10. Meiosis I
Metaphase I: Homologous chromosomes line up at center of cell
Anaphase I: Homologous chromosomes separate and pulled to opposite ends of cell, chromosome # is reduced from 2n to n

11. Meiosis I Telophase I: Chromosomes reach poles
Each pole contains only one chromosome of the original homologous chromosomes

12. Meiosis II Prophase II: chromosomes condense
Metaphase II: HAPLOID (n) number of chromosomes line up at the equator

13. Meiosis II Anaphase II: sister chromatids are pulled apart
Telophase II: chromosomes reach poles and nuclear membranes and nuclei form

14. Meiosis II
Chromosomes DO NOT replicate between I and II  end result is 4 haploid cells, each with n number of chromosomes

15. MEIOSIS V MITOSIS

16. Sexual vs. Asexual Reproduction*
The organism inherits all of its chromosomes from one parent
Individual is genetically identical to its parent

17. Meiosis in males vs females
In females it is called oogenesis
Begins while in utero during the third trimester and stops until puberty.
Results in 1 healthy egg (ovium) and 3 polar bodies (cells with a nucleus and no cytoplasm) when completed
It is only complete after fertilization has occurred.

18. Meiosis in males vs females
In males it is called spermatogenesis
Doesn’t occur until puberty
Results in 4 haploid sperm cells.
Completed every ~74 days.

19. Meiosis in males vs females
Completed Monthly

20. Gregor Mendel Genetics: the study of heredity
Heredity: the passing of traits from parent to offspring (INHERITANCE)
Gregor Mendel: Father of Genetics
Austrian Monk who experimented with garden peas in 1866, he noticed certain traits seemed to be passed from one generation to another

21. Gregor Mendel Mendel worked with peas, which self-fertilize
Some varieties always made green seeds, some always made yellow seeds, so he cross-pollinated the peas by hand
Parent Generation (P): 1st line of crosses
First Generation(F1): offspring of the parent generation
F2 Generation: second cross, using the F1 offspring

23. Alleles
He determined there must be TWO forms of a gene controlled by different factors
Alleles: alternative form of single gene
For example: height
Tall or short
Alleles are NOT genes, they are two different versions of one gene!

24. Alleles Alleles are either dominant or recessive
Dominant: represented by a capital letter (T = tall)
This is the trait that is seen
Recessive: represented by a lowercase letter (t = short)
This trait is not seen, it is masked by the dominant allele ~ it’s there, just hidden!

25. Alleles If the dominant allele is present, it will show up – DOMINANCE
There must be 2 recessive alleles in order to show up
We inherit an allele for a specific gene from each parent

26. Alleles Homozygous: individual inherits 2 of the same allele
TT – homozygous dominant OR tt – homozygous recessive
Heterozygous: individual inherits 2 different alleles, one dominant and one recessive Tt
Since the dominant allele is present, it will show

27. Genotype & Phenotype Genotype: organism’s allele pairs
Heterozygous, homozygous dominant, or homozygous recessive
Phenotype: observable appearance of genes

28. Putting it all Together…
GENOTYPE (HETEROZYGOUS) Tt =
Tall
ALLELE
ALLELE
PHENOTYPE

29. Law of Segregation Two alleles for a trait separate during meiosis
Each gamete will have a different allele
They will be reunited during fertilization

30. Law of Independent Assortment
When gametes are made during meiosis each only gets one copy of a gene
This is random; the inheritance of one gene does not influence the inheritance of another gene; they are independent
Every person with brown hair doesn’t have brown eyes
Some genes are inherited together (LINKED) because the genes are very close to each other on the chromosome.
people with red hair are also fair-skinned.

31. Punnett Square
Used to predict the possible offspring between two known genotypes
Monohybrid: crossing one trait at a time
Dihybrid: crossing two traits

32. Punnett Square
Parent 2 – Pure Tall
F1 Generation
Parent 1- Pure Short

34. T t TT Tt T Tt tt t Tongue Rolling Dominant Trait ~ T
2 parents are heterozygous (Tt) for the trait
What possible phenotypes will their children have? T t TT Tt T
Tongue roller
Tongue roller Tt tt t
Non-tongue roller
Tongue roller

35. Punnett squares
Determining ratios

36. Punnett Square—Dihybrid Cross
Chapter 10
Sexual Reproduction and Genetics
10.2 Mendelian Genetics
Punnett Square—Dihybrid Cross
Four types of alleles from the male gametes and four types of alleles from the female gametes can be produced.
The resulting phenotypic ratio is 9:3:3:1.

37. Punnett Square

38. 10.3 Gene Linkage and Polyploidy
Chapter 10
Sexual Reproduction and Genetics
10.3 Gene Linkage and Polyploidy
Genetic Recombination
The new combination of genes produced by crossing over and independent assortment
Combinations of genes due to independent assortment can be calculated using the formula 2n, where n is the number of chromosome pairs.

39. 10.3 Gene Linkage and Polyploidy
Chapter 10
Sexual Reproduction and Genetics
10.3 Gene Linkage and Polyploidy
Gene Linkage
The linkage of genes on a chromosome results in an exception to Mendel’s law of independent assortment because linked genes usually do not segregate independently.

40. Polyploidy is the occurrence of one or more extra sets of all
Chapter 10
Sexual Reproduction and Genetics
10.3 Gene Linkage and Polyploidy
Polyploidy
Polyploidy is the occurrence of one or more extra
sets of all
chromosomes
in an organism.
A triploid organism, for instance, would be designated 3n,
which means that
it has three complete sets of chromosomes.