Lec 10 - Genotype, Phenotype Flashcards
briefly explain how DNA, genotype and phenotype are linked ?
DNA is Replicated DNA is transcribed into RNA RNA codes for the protein Genes are coded on our DNA we have different alleles for genes our genotype codes for our phenotype This leads to different expressions in the phenotype our proteins and also physical characteristics
Define genotype, and phenotype
The genotype of an organism is defined as the sum of all its genes.
The phenotype of an organism is the observable physical or biochemical characteristics of an organism,
Both can be determined by both genetic make-up and environmental influences such as lifestyle and chemicals ect
how are genes and alleles related
each individual has two copies of a gene - maternal and paternal
each individual has two alleles of a gene
many different alleles within a population
Define Homozygous, heteroxygous and hemizygous
homo - the two alleles of a gene are the same
hetero - two alleles of a gene are different
hemi (one/singular)- only one allele of a gene on the X chromosone - males only
define and explain dominant and recessive traits
dominant allele in a heteroxygote determines phenotype (what is expressed)
recessive allele is non-dominant and not expressed in a heterozygote
A - dominant
a- reccesive
Aa genetype - A is expressed
Explain Co-dominance
using blood type as an expamle
when two alleles do not dominate over each other then they are co dominant and a new phenotype is expressed
blood - human isoglutamin gene codes for glycoproteins on the surface of the RBC’s
three alleles A, B, O (IA/IB/IO)
Both A and B dominate over O (recessive)
A and B are codominant
4 possibilities in genotype - A (AA or AO),
B(BB or BO),
AB(AB),
O(OO)
draw an example pedigree
Best way to practice this is group work and review lectures
draw it fool
What do the following terms mean ? Autosomal Sex linked Mitochondrial Ploygenic Autosomal Reccesive Autosomal Dominant X linked recesicve X linked dominant Y linked
Autosomal - gene is on a non sex linked chromosone
Sex linked - on the X/Y sex chromosone
Mitochondrial - coded for and carried in mitochondria (we only ever inherit our mothers mitcohondria - so always passed on via mother - father cannot pass on)
Ploygenic - complex - many genes involved to produce phenotype
Autosomal Recessive - aa
Autosomal Dominant - AA or Aa
X linked recessive - Xa Xa or Xa Y
X linked dominant - XA Y or XA Xa or XA XA
Y linked - carried on Y chromosone - only men can inherit this
what is cystic fibrosis’ inheritance pattern ?
Autosomal Recessive - males and females equally affected by any autosomal trait
2 parental carriers allow disease to skip a generations phenotype
what is Huntington’s disease inheritance pattern ?
Autosomal dominant - Aa will express in phenotype
cannot skip generations
what is Haemophillia A inheritance pattern ?
X linked Recessive
males more common to disease - cannot pass it on
Females often heterozygous carriers
X linked dominat - how do you work out what is inherited
bonus info - rett syndrome
draw a punnet square
what is polygeninc
Ploygenic - complex - many genes involved to produce phenotype
ie need 3 enzymes to process intermediates to produce the needed product - each enzyme has its own coding gene
Explain how albinism works
Polygenic inheritance
Gene A
Alleles A and a
Gene B
Alleles B and b
genotype can be
AABB, AABb, AaBB, AaBb, aaBB, AAbb, Aabb,aaBb aabb
Albinism is recessive - you only need one of the two genes to be homozygous recessive and you express albinsim in phenotype
so aaBB, AAbb, Aabb, aaBb, aabb will all express albinsim
ie AaBb will not
explain the difference between linked and not linked genes in inheritance (polygenic)
use notes to practice inheritance on this
genes on same chromosome are linked,
different chromosomes are not linked
linked genes do not show independent assortment at meiosis
ratio of gametes in linked genes is not 1:1:1:1
it is 1:1:1:1 in linked genes
recombination frequency between two linked genes is dependent on gene distance
close genes are tightly linked
far apart genes on the same chromosome behave almost like unlinked
