Biology AQA inheritance

Human cells have…

23 pairs of chromosomes

Mitosis

One cell duplicates into two other identical cells

Gametes

Sex cells-Single(Only have 23 pairs of chromosomes)

Sperm and Egg

Meiosis

Production of gametes

Produces genetically variated cells

Sexual reproduction

Involves mixing of genetic info→Variation

Fertilisation →Fusion of sperm and egg and mitosis

Asexual reproduction

Only one parent→No gametes

No mixing of genetic info→Offspring=Genetically identical=(Clones)

Meiosis doesn’t take place→Mitosis

Key words

Dominant(C) alleles are always expressed

Recessive(x) alleles are remain dormant unless it is paired with another recessive gene

Homozygous=Two of the same genes(TT/tt)

Heterozygous=Variated genes(Tt)

Punnet squares

Draw a grid like shape

add the genes

go across and down

count the given gene’s %

Embryo screening

Take embryos to look into their genes to identify if theres any signs of genetic disorders

If theres those signs,they MIGHT decide to discard the embryo

Positives of embryo screening

Reduces suffering

Cost effective

Negatives of Embryo screening

Claims people with genetic disorders are discluded(Prejudice)

Future screenings for other traits

Variation

The difference in characteristics between species in a population

Factors which affect variation

Genetic=Born with it,remains on you

Environmental=You do something to make that happen

Both=Caused by traits you have and made

Examples

Genetic=Eye colour,Blood group and Skin colour

Environmental=Tattoos,scars and tanning.

Genotype

Alleles that an organism has for a particular characteristic

Phenotype

The observable physical properties of an organism

Classification systems

Orders species of organsims

Linnaean and Woese models

Linnaean system(Carl Linnaeus)

Order based on bone structure and characteristics

Order:

Kingdom

Phylum

Class

Order

Family

Genus

Species

Way to