heredity Flashcards
gene
a unit of inheritance on a particular locus of a chromosome.
it is made up of a sequence of nucleotides that codes for a specific protein that controls a certain characteristic
alleles
alternative forms of a same gene
they occupy the same positions on a homologous chromosome
chromosome
has many genes along its length
phenotype
the physical appearnace of an organism
genotype
the genetic make up of an organism
homologous chromosomes
a pair of chromsomes that have the same shape, length and same order of gene loci
gene loci
position of a gene on a particular chromsome
homozygous
if two alleles containing the same trait are identical
heterozygous
if two alleles containing the same trait are different
pure bred
indiviuals that are homozygous at a particular gene locus
selfing
fusion of nuclei of female gamete and nuclei of male gamete from the same individual
co-domimance
when both alleles controlling a trait equally expresses themself in a phenotype in an organism in the heterozygous condition
diff between AS and NS (5)
AS:
- varieties produced by selective breeding
- selection force is by man
- relatively fast process
- positive to man
- parents are consciously chosen for desirable traits
NS:
- varieties produced by mutations
- selection force is envt
- v slow process
- negative or positive to man
- parents are not consciously chosen
diff btwn discontinuous variation and continuous variation (4)
dis:
- a few clear cut phenotypes
- contrlled by 1 or few genes
- genes dont show addtiive effect
- not affected by envt conitions
cont:
- deals with a range of phenotypes
- controlled by many genes
- show additive effect
- affected by envt condtiions
mutagens
radiation: uv rays, xray, gamma ray, alpha and beta radiation
chemicals: lysergic acid diethylamine, mustard gas, formaldehyde
fromation of new species
Even though there are high reproductive rates, number of organisms in a population remains instant due to enironemntal factors such as competition for resources and predation
Mutation genes may result in formation of new alleles and some of tem may be advantageous
able to camouflage more?? context
When competition arises, nature selects those that have more advantageous favorable traits to survive such as adaptable to changes in environment, disease resistant, more competitive
so more of them survive as less (context) of them die/are eaten
those with the more advantageous favorubal traits will survive to repoudctive age and reproduce and pass down their favourable traits to their offspring
As a result, the frequency of these traits will increase in the population
After many years, new traits form and gives rise to new species
artificual selection
Method used by man to purposefully produce offsprings with desirable traits by intentionally choosing those exhibiting the desirable traits
Those with desirable traits are artificially selected by selective breeding
Cross breed two animals -> hybridisation -> new variety that carries both desirable traits
To increase chances of the organism inheriting both traits -> inbreeding -> select two organisms that are closely related
-ve effect: increase inherited diseases
down’s syndrome
Change in chromosome number - chromosome mutation during meiosis 1 or 2
1 extra copy of chromosome 21
47 chromosomes in diploid cells
Mental retardation, heart defects
a person has 2 sets of HC, each inherited from a parent. an extra set of chromosome (2set) is oackaged within a single gamete. zygote formed when this gamete fuses with another gamete -> 3 sets of chromosome 21
sickle-cell anaemia
Change in structure of gene in DNA - gene mutation
caused by recessive allele
sickle cell sahped red blood cell
RBC unable to transport oxygen at a faster rate
ppl die at younger age
multiple alleles def
when a gene controlling a particular trait has 3 or more alleles
e.g. blood group
does natural selection lead to gene mutation occuring?
NO
mutations benefits
increase genetic variation to adapt to envt conditions
evolution bc of frequncy imcrease
mutation meaning
the chnage in nucleotide sequenc of gene, resukting in expression of a polypetide that differs frm nonral polypeptide
