BIOLK101 Chapter 14/15 - Mendel and the Gene Idea

gene

functional unit of heredity

phenotype

observable characteristics

genotype

alleles, do not show as outward characteristics

locus

position on a chromosome

allele

one of two or more alternative forms of a gene

Mendels 2 laws

law of independent assortment

law of segregation

law of independent assortment

homologous chromosomes randomly distributed at metaphase plate so mom/dad homologous are mixed and assorted to each gamete

law of segregation

When gametes form, alleles (homologous chromosomes) separate and only 1 allele is found in each

Parental generation

mendels cross pollinates 2 true breeding plants

F1 generation

100% dominant shows but heterozygous

F2 generation

3:1 dominant to recessive

3 of Mendel’s hypothesis

every trait controlled by 2 heritable parents

recessive and dominant

allele segregation

allele

each form of genes/heritable factors

Allele segregation

alleles segregated into eggs and sperm when homologous separate during Meiosis I

When does Independent assortment happen?

Metaphase I

when does segregation happen?

anaphase I —> telophase I

Cystic fibrosis

mutation in CFTR/chloride channel

sickle cell

mutation in hemoglobin gene

Carrier of Sickle Cell

resistant to malaria

Carrier of Cystic fibrosis

resistant to cholera

Sickle Cell + Cystic Fibrosis

both co dominant alleles

achondroplasia

dwarfism

mutation in FGFR3 (fibroblast growth factor receptor 3)

polydactyly

extra fingers/toes

huntington’s chorea

mutation of huntingtin heterozygous

nervous system degenerates

marfan’s syndrome

fibrilling deficiency in connective tissue affecting skeletal, eyes, CV system

pleiotropic

single gene or variant influences multiple phenotypes

progeria

mutation of Lamin A, leading to aging

spontaneous disorder

dihybrid cross

2 independent events occurring together

Ratios of dihybrid crosses

9:3:3:1

incomplete dominance

2 incomplete dominant alleles

e.x. red and white flower cross and show pink

cause of incomplete dominance

one allele lacks ability to produce pigment and visible in phenotype

ABO blood

multiple alleles. co dominance

ii blood

O blood

codominance/multiple alleles

both traits expressed in same organisms, and more than 2 alleles

how many alleles do women have for all genes

2

2 X chromosomes

3 X linked allele mutations

colour blindness

duchenne muscular dystrophy

hemophilia

duchenne muscular dystrophy

lack dystrophin

hemophilia

affect children lacking blood clotting factor VIII