inheritance - monohybrid crosses

gametes

sperm and egg haploid (n) cells produced in meiosis

- only have ONE copy of each chromosome

diploid (2n)

used to describe a nucleus that has chromosomes organised into PAIRS of homologous chromosomes

- most cells in humans

who is known as the father of genetics

Gregor Mendel

punnet grid

used to analyse results of genetic crosses

F1 generation

created a monohybrid cross between yellow-seed plants and green-seed plants

allele

different versions of genes - dominant or recessive

genotypes

symbolic representation of the pair of alleles possessed by an organism (typically represented as two letters).

homozygous

refers to having two identical alleles of the gene (identical letters)

hetreozygous

refers to having two different alleles of the gene (different letters)

dominant

the form of the trait always appears when the individual has it

recessive

the form of a trait that appears only when the individual has two alleles for it

carrier

an individual who has a recessive allele of a gene that does not have an affect on the phenotype.

phenotype

is the observable characteristics or traits of an organism.

exclusive genetically produced phenotypes

ABO blood type

Genetic conditions (Huntington's disease, cystic fibrosis, colour blindness)

exclusive environmentally produce phenotypes:

Learned behaviour (humans learning math, birds learning songs)

Acquired physical traits (scars, muscles from weight lifting)

Interaction between environment and genetics phenotypes:

Height in humans (maximum height is genetic, but poorly nourished may not reach it)

Cancer (has genetic components, but often triggered by mutagens)

punnett grid

used to show how the alleles of parents are split between their gametes and how new outcomes of alleles show up in their offspring

- shows all the possible combinations of genetic information for a particular trait in a monohybrid cross

Paternal generation (p generation)

the first of any genetic cross - purebred so the alleles are known

First filial generation (F1):

the first generation produced by the parents.

Second filial generation (F2 generation)

the product of the generation from the crossing of the F1 generation

phenotype plasticity

an organisms ability to express its phenotype differently depending on the environment - an effective way of adapting

what is PKU

Phenylketonuria is an example of a genetic disease due to a recessive allele.

- recessive because a carrier with one PKU allele can still produce the functioning enzyme because they have a normal allele

what causes PKU

Caused by mutations in the autosomal PAH gene that results in low levels of the enzyme phenylalanine hydroxylase.

Phenylalanine hydroxylase (enzyme) converts the amino acid phenylalanine into tyrosine (non toxic),

- phenylalanine can become toxic if there is an abundance of protein in a child's diet resulting in high levels of the amino acid and impaired brain development.

- chromosome 12