3.4 + 10.2 inheritance

mendel’s laws

mendel’s laws

principle of dominance: dominant allele masks the recessive allele

law of segregation: alleles separate in equal numbers into different gametes due to meiosis, such that each gamete only carries 1 allele for each gene.

law of independent assortment: 2 or more pairs of alleles (each determining a diff characteristic) segregates independently of e/o during meiosis.

genetic diagrams

1. parental phenotype

2. parental genotype

3. meiosis

4. gametes

5. fertilisation

6. f1 phenotype & genotype

7. meiosis

8. gametes

9. punnet grid

10. f2 genotype

11. f2 phenotype

12. f2 phenotypic ratio

test cross

use homo recessive, to determine if a dominant-displaying phenotype is homo dom or heterozygous

if all offspring are dominant phenotype, then parent is homo dom

if half offspring are dom phenotype & other half are recessive phenotype, then parent is hetero

codominance

where codominant alleles both affect the phenotype when present in a heterozygote

eg. blood type

sex linked genes

XaXA Y

x-linked genes XAXa

the association of a characteristic w gender

1. hemophilia: XH normal, Xh hemophilia. the absence of clotting factor

2. red-green colour blindness: recessive — Xb or XB

pedigree charts

1. autosomal or sex-linked:

   1. if 50/50 bw men & women, autosomal

   2. if most males are affected, sex-linked

2. dom or recessive disease:

3. autosomal:

   1. idk go check ur notes im too lazy

mutations

mutagens: increase risk of mutation — uv rays, gamma rays, chemicals — tar, asbestos

mutation in an oncogene (controls cell cycle & division) → malfunction in control of cell cycle → uncontrolled cell division → tumour

linked genes

genes located on same chromosome

are inherited tgt

for diagram drawing thing, must do the lines !!

do not segregate independently during meiosis

dihybrid vs monohybrid inheritance

monohybrid: inheritance of 1 characteristic

dihybrid: 2 characteristics

ratios: IMPT!!

monohybrid 3:1 dom:rec

dihybrid

• hetero x hetero — 9:3:3:1 dom recomb rec

• hetero x homo — 1:1:1:1

dihybrid: linked genes

• w/o crossing over — homo dom x homo rec 3:1 dom:rec

• w crossing over — no fixed ratio

discontinuous vs continuous variation

discontinuous: discrete phenotypes, limited forms of variation. controlled by 1 or 2 major genes. not affected by environment

continuous: normal distribution curve. may have >2 alleles that are codominant. controlled by many genes (polygenic)

polygenic inheritance

phenotype is the result of the additive effect of 2 or more genes

greatly influenced by environment

small differences bw phenotypes — continuous variation

eg. skin colour in humans, controlled by 3-4 genes inherited independently

chi-squared tests

null: no signif diff

alt: signif

determine expected values based on fixed ratio

chi-squared formula sum of (observed-expected)2/expected

df = n-1

p>0.05: accept null — no signif diff, deviation is due to chance

p<0.05: reject null 00 signif diff, deviation is not due to chance