monohybrid inherritance

genetics

the study of heredity and variation

heredity

passing on characteristics from parents to offspring

variation

the differences between members of species

species

organisms capable of interbreeding and producing fertile offspring

gene

unit of heredity , composed of dna ; controls development of a characteristic

locus

position of a gene on a chromosome

alleles

alternative forms of the same gene

genotype

the genetic make - up of an organism

phenotype

the visible expression of the genotype ; depends on the genotype and effect of the environment

dominant

an allele that is expressed when it is homozygous and heterozygous

an allele that masks the expression of thee partner allele

recessive

an allele that is only expressed when it is homozygous

an an allele whose expression is masked by a dominant allele

incomplete dominance

the heteerozygous genotype gives a different phenotype from either of the homozygous genotypes

neither allele is fully expressed in the heterozygote

homozygous

pair of identical alleles for a characteristic

heterozygous

pair of different alleles for a characteristic

gametes

haploid sex cells that fuse during sexual reproduction to form a diploid zygote

monohybrid inheritance

the study of the inheritance of one charcteristic

mendel 1st law - law of segregation

characters are controlled by a pair of factors that seperate during gamete formation - only one factor of each pair is present in a gamete

dihybrid inheritance

study the inheritance of two different characteristics at the same time

mendel 2nd law - law of independent assortment

during gamete formation either one of a pair of alleles may enter a gamete with either one of another pair of alleles

linked genes

genes on the same chromosome that are inherited together

linked genes do not show independent assortment

they do not obey mendels 2nd law

when genes are linked , all the progeny show the same combination of characters as the parents

autosomes

chromosomes that do not determine sex (22 pairs)

sex chromosomes

pair of chromosomes that determine sex

sex linked genes

genes carried on the sex chromosomes

most sex linked genes are located on the x chromosome

sex linked characteristics in the human

colour vision / blood clotting

non nuclear dna

- dna found in the mitochondria and chloroplasts

when these organelles replicate during cell division they pass on their dna to the daughter organelles

examples of non nuclear inheritance

human - some nervous disorders

plants - yellow/ white patches on leaves ( veriegation )