6.2 Monogenic Inheritance Flashcards
variation is the phenotypic differences between who?
organisms of the same species
what 4 things can variation be the result of?
- independent assortment of homologous chromosomes
- crossing over in meiosis
- random fertilisation of gametes
- mutation
monogenic inheritance explains what?
how genes are passed one generation to the next
monogenic inheritance - the basic laws by which characteristics were inherited were established by who?
Mendel
scientist and monk in the 19th century
(monohybrid inheritance) inheritance of a single characteristic is controlled by what?
a single gene
(monohybrid inheritance) a single gene can have how many alleles?
multiple
(monohybrid inheritance) what 3 things can alleles be?
dominant
recessive
co-dominant
(monohybrid inheritance) what is a gene?
specific length of DNA occupying a position on a chromosome known as a locus
(monohybrid inheritance) what is a chromosome?
linear sequence coding for many genes
(monohybrid inheritance) what does it mean if genes are homozygous?
same alleles
(monohybrid inheritance) what does it mean if genes are heterozygous?
different alleles
(monohybrid inheritance) what do chromosomes exist in?
pairs
one chromosome originally from the mother
one chromosome originally from the father
- when performing a genetic cross you first need to state what?
phenotypes of both the parents
- when performing a genetic cross you need to then state what of the parents?
genotype
assign letters to represent alleles
3.when performing a genetic cross, after you have stated the genotype what do you have to state of the parents?
gametes
- when performing a genetic cross you use what type of square? and what does it show?
punnet square
show random fusion of gametes
- when performing a genetic cross, after you have done the punnet square you state what?
proportion of each genotype produced amongst the offspring
- when performing a genetic cross, you then state the corresponding what?
phenotype for each genotype
what did mendel carry out many of his experiments on?
pea plants
when a homozygous green pea plant is crossed with a homozygous yellow pea plant which allele is dominant?
allele for green pea plant
what are true breeding/pure breeding organisms?
organisms containing homologous alleles for a particular gene
co-dominance occurs when 2 alleles occur for a gene, both of which are what?
dominant
(co-dominance) what happens to the alleles in the phenotype?
both are expressed
(co-dominance) give an example of an organism in which co-dominance is found:
colour of snapdragon flowers
(co-dominance - snapdragons) the allele which codes for red flowers codes for production of what?
an enzyme catalysing production of the red pigment
(co-dominance - snapdragons) the allele coding for white flowers codes for what?
altered version of the enzyme which doesn’t catalyse production of the pigment so flowers are white
(co-dominance - snapdragons) when do red flowers occur?
when the plant is homozygous for the allele coding for the red pigment
(co-dominance - snapdragons) when do white flowers occur?
when the plant is homozygous for the allele coding for the white pigment
(co-dominance - snapdragons) when do pink flowers occur?
when the plant is heterozygous - allele for red pigment produces enough for flowers to be pink
(co-dominance - snapdragons) how are co-dominant alleles represented?
uppercase letter with a smaller lowercase letter to indicate colour
(sex linkage) some characteristics are carried on which chromosomes?
sex chromosomes
(sex linkage) why do are there a number of genes on the X chromosome men have only one copy of?
Y chromosome is smaller than the X
(sex linkage) why may characteristics caused by recessive alleles on the X chromosome appear more frequently in men?
because it is missing on the Y in males - females may have dominant allele present on another X chromosome
(Sex linkage) what is a sex linked genetic disorder?
Haemophilia
(Sex linkage) what happens in haemophilia?
Blood clots slowly due to lack of protein blood clotting factor
Small cuts could be fatal
(Sex linkage) if a male inherits the recessive allele for haemophilia on their X chromosome will they inherit it?
Yes
Don’t have the corresponding dominant allele on their Y chromosome
(Sex linkage) do females who are heterozygous for haemophilia suffer?
No they are carriers
(Multiple alleles) how many alleles does a gene have to be classed as a multiple allele?
3+
(Multiple alleles) how many alleles can be present in an individual?
2
(Multiple alleles) what is determined by a gene with multiple alleles?
Blood group
(Multiple alleles) blood group - what does immunoglobulin gene code for?
Production of different antigens on surface of RBCs
(Multiple alleles) blood group what does Ia result in?
Production of antigen A
(Multiple alleles) blood group - what does Ib code for?
Production of antigen B
(Multiple alleles) blood group - what does Io code for?
Neither antigen
(Multiple alleles) blood group - which alleles are co dominant?
Ia and Ib
(Multiple alleles) blood groups - which allele is recessive?
Io
(Determining sex) which chromosome determines sex?
23rd
(Determining sex) which chromosome carries the gene causing the embryo to develop as male?
The Y chromosome
(Determining sex) how is the sex of the offspring determined?
By the sperm fertilising the egg containing an X or Y
(Dihybrid inheritance) what is dihybrid inheritance used to show?
Inheritance of 2 characteristics caused by two genes
(Dihybrid inheritance) give an example of dihybrid inheritance?
Phenotype of pea plants
Yellow or green
Round or wrinkled
