Topic 3 – Genetics-Inheritance Flashcards
what is a chromosome?
a long coiled molecule of DNA that carry genetic information in the form of genes
define gene
section of DNA that codes for specific sequence of amino acids which undergo polymerization to form a protein
what are alleles?
different versions of same gene
define genotype
organism genetic composition, describes all alleles
define phenotype
organism observable characteristics due to interactions of genotype and environment
define homozygous
having 2 identical alleles FF or ff
define hetrozygous
having 2 different alleles Ff
what is a dominant allele?
describes allele that is always expressed, represented with capital letter F
what is a recessive allele?
allele that is only expressed in absence of dominant allele
represented with a small letter e.g. f
what is monohybrid inheritance?
inheritance of a single gene
what is the problem with single gene crosses?
most characteristics are controlled by multiple alleles rather then one
what are sex chromosomes?
pair of chromosomes that determine sex
males have X and a Y chromosome
females have two X chromosomes.
why does the inheritance of Y chromosome mean embryo develops into a male?
testes development in embryo is stimulated by a gene present of Y chromosome
other then a punnett square, how else monohybrid inheritance be represented?
using family pedigree
what is a sex linked characteristic?
a characteristic that is coded for by an allele found on sex chromosome
why are majority of genes found on X chromosome rather then Y?
X chromosome is bigger then Y, so more genes are carried on it
why are men most likely to show phenotype for a recessive sex linked trait then wommen?
many genes are found on X chromosome that have no counterpart on Y chromosome.
Women have 2 alleles for each sex linked gene whereas men often have 1, so only 1 recessive allele is required to produce recessive phenotype in males
give an example of a characteristic that is determined by more then 1 allele?
blood groups is determined by 3 alleles: Ia Ib Io
Name 4 different blood groups
A, B, AB, O
what are codominant alleles?
alleles that equally contribute to organism phenotype. expressed to equal extent.
describe codominance in blood groups
IA and IB are codominant
IA IB gives blood group AB
Why does IA IO give blood group A?
Io is recessive to IA
IA is dominant and expressed given to blood group A
what are possible genotypes for B?
Ib or Io
Ib or Ib
what is genotype for blood group O?
Io Io
