Lec 14-16 Flashcards
Meiosis
Meiosis I: homologous chromosomes separate, sister chromatids stay together, two daughter cells
Meiosis II: daughter cells divide again, sister chromatids separate,
creates 4 daughter cells
Genetic variation
Crossing over: parental and maternal homologs exchange genetic material, occur on genes far apart from each other
Independent assortment: chromosomes line up independently from each other at the metaphase plate, random alignment of chromosomes
A father is carrying the recessive allele for male-pattern baldness gene on his X chromosome. A mother does not carry that allele at all. What are the chances that their son will show the phenotype for male pattern baldness?
a) 0 chance
b) ¼ chance
c) ¾ chance
d) ½ chance
0 chance because men pass on Y chromosomes, not X
Genotype & phenotype
Genotype: genetic makeup
Phenotype: observable trait
Aa x Aa
Combinations & genotypic, phenotypic ratio?
Combinations: AA, Aa, Aa, aa
Genotypic ratio: 1:2:1
Phenotypic ratio: 3:1
Non mendelian pattern of inheritance
-genes located on sex chromosomes
-linkage: tendency of alleles from different genes to be inherited together because they are located close to each other
Transcription & translation
Transcription: genes are transcribed into mRNA by mRNA polymerase
Translation: ribosome reads mRNA and manufactures the resulting protein by recruiting the correct amino acids and bonding them into a chain
Template & coding strands
Template: 3’ to 5’, complimentary to mRNA
Coding: 5’ to 3’, identical to mRNA (t becomes u)
Codon
3 mRNA bases, specifies an amino acid
Transcribe the template strand
3’ AGCTGGCAATTC 5’
3’ UCGACCGUUAAG 5’
Transcribe the coding strand
5’ TGACCTGCGATT 3’
5’ UGACCUGCGAUU 3’
Mutations in mRNA, amino acids
Silent: doesn’t change amino acid, has no effect
Nonsense: adds premature stop codon, has severe effect
Missense: changes amino acid, if they have the same properties (conservative) it’ll have a mild effect, if they have different properties (non-conservative) it’ll have a more severe effect
What mutation is this?
Original: CUC
Mutated: CCC
CUC codes for Leu which is nonpolar, CCC codes for Pro which is also nonpolar so it is a conservative missense
What mutation is this?
Original: GUC
Mutated: GUG
They code for the same amino acid so it is a silent mutation
What mutation is this?
Original: AGU
Mutated: CGU
AGU codes for a polar amino acid and CGU codes for a basic amino acid, so it is a non-conservative missense
