Genetics Pg 5

Meiosis 27. Meiosis is important to sexual reproduction because it ensures that the gametes have only ½ of the DNA as a regular (somatic) body cell so that when two gametes come together in fertilization it equals 1. It is also important for genetic diversity, no two gametes are the same. Humans sperm-23 chromosomes + egg- 23 chromosomes = 46 chromosomes 28. Meiosis creates the gametes (sex cells)

#29 Sexual 2N diploid 1N haploid 2 4 Meiosis  ​ Meiosis Type of Reproduction (asexual or sexual)​ ​ Chromosome number of parent cell​ (1N=haploid or 2N=diploid)​ Chromosome number of daughter cells​ Number of Cell Divisions​ Number of Daughter Cells​ When does DNA replication take place?​ Sexual 2N diploid 1N haploid 2 4 Interphase during Meiosis 1

Vocabulary #46 dominant – written as a capital letter, this trait will show in Mendelian genetics recessive – written as a lower case letter; only will show if two recessive alleles are present   homozygous – SAME alleles; TT or tt heterozygous – DIFFERENT alleles; Tt genotype – letter combination that show the genes; TT, Tt, tt phenotype – physical description; tall or short Allele- a form a gene. Can be dominant or recessive

#47 In a genetics laboratory, two heterozygous tall plants are crossed. If tall is dominant over short, what are the expected phenotypic results? Tt x Tt T t T t Phenotype: 75% TALL TT, Tt 25 % SHORT tt 3:1  TT Tt tt

B Tt Tt tt tt x Tt t t T t 50% short 50% tall 1:1 If one homozygous short plant is crossed with a heterozygous tall plant, what percentage of the offspring will be short? tt x Tt t t T t 50% short 50% tall 1:1  Tt Tt tt

RRdd x RrDD F first Rd RD O outside Rd RD I inside Rd rD L last Rd rD #48 RRdd x RrDD F first Rd RD O outside Rd RD I inside Rd rD L last Rd rD

Rd Rd Rd Rd RD Genotypes: RRDd-50% RrDd-50% rD Phenotypes: 100% red eyes and dark fur RRDd rD RrDd rD

#49 Incomplete dominance the two traits blend when both are present RW x RW Two pink flowers are crossed R W R W 25% RED-RR 50% PINK-RW 25% WHITE-WW RR RW WW

#50 Co-Dominance Both traits show up when both are present A A A B 50% AA IA IA IA IB

Explain how it is possible for a man with type a blood and a woman with type b blood have a child with type o blood. O (i) blood is recessive, so if the male is AO and the female is BO then a child could have OO

#51 Sex linked traits are carried on the sex chromosome X Males have one X, females have two X’s Therefore a male only needs one allele to have the trait, but females need 2 alleles to have the trait. This makes is more rare for a female to have a sex linked trait. But females can be carriers

#53 Sample Sex-linked trait Question: Color blindness is a sex-linked recessive trait. A mother with normal color vision and a color blind father have a color blind daughter. Which of the following statements is correct? All of their daughters will be color blind. The mother is a carrier of the color blindness gene. All of their sons will have normal color vision. All of their sons will be color blind.