Human Genetics 1 & 2 Flashcards
describe dominant allele
mask other traits (Written in capital) (one copy needed)
describe recessive allele
is covered when dominant is present (Written with lowercase) (two needed)
what is a purebred
homozygous (two identical alleles e.g. aa, AA, for particular gene)
what is hybridisation
crossing of two purebred plants
what are the 3 generations according to mendel
P gen (parental)
F1
F2
what is a genotype
combination of genes in individual (written underlined or in italics)
what is a phenotype
physical trait and depend on genotype
What probabliitys do you include in punnet squares
prob of geno + pheno
What is mendels first law
law of dominance
- only one trait is shown= dom trait
what is a dihybrid cross
crossing with two genes/traits e.g. yellow/green + round/wrinkled
mendels second law
law of segregation
inherited traits exists in alleles
- this pairs segregate + sex cell only receives 1
mendels third law
law of independent assortment
- alleles distributed indecently from one another
what are monogenic traits
- Traits (genes/alleles) with simple Mendelian inheritance
- Characteristic/trait determined by a single gene/allele
- One locus on a chromosome
what are monogenetic diseases classified into
• Autosomal vs X-linked
o Is the gene located on an autosome or sex chromosome?
• Dominant vs recessive
o How many alleles are necessary to express the phenotype?
when determining mode of inheritence= whats the first step
do all affected individuals have an affected parent
Yes= dom
No= rec
when determining mode of inheritence= if dom, how to determine whether auto or x linked
father to son transmission
yes= autosomal
no= x linked
when determining mode of inheritence= if rec, how to determine whether auto or x linked
only males affected?
yes- x linked
no= auto
if sexes are equally affected in monogenic disease, is it x linked or auto
auto
what is the interbreeding coefficient
prob that genes at randomly chosen location are identical by descent
what is interbreeding depression
Reduction in performance and viability due to reduced genetic variation with increasing interbreeding levels
what is the problem with interbreeding
- Breeding from small gene pool can increase autosomal recessive disorders in a line if there is a carrier in that line
how does green eyes work
2 alleles (OCA2- Brown, blue, Gey- Green, blue)
in OCA2 and Gey what is dom and rec
Brown (B) dom over Green (G) and blue (b)
Green (G) dom over blue (b)
What do the genes that determine eye colour actually function as/ express
- Melanin // amount coded determines eye colour
- Amount of pigment melanin found in stroma of iris determines eye colour
- Lots of melanin= brown, less= green, little to no= blue
what is the non functional melanin gene
blue
how does blue eyed parents= brown eyes child
OCA2= OCA2 + HERC 2
- needs HERC2 to turn on OCA2 which then makes pigment
- if either not working = blue rather than intended dom brown // carrier of brown
what sort of trait is eye colour
polygenic
explain polygenic inheritance
- Characteristic/trait result of combined effect of several genes
- results in continuous range of small differences in given trait among individuals
explain incomplete/partial dom
- intermediate inheritance, = neither of two alleles are entirely dominant
- heterozygous indiv. exhibit a blending of two traits to produce intermediate phenotype b./w that of two
- homozygous parents
explain co-dominance
- Occurs when pairs of non-identical alleles are both expressed equally in the phenotype of a heterozygous individual
- No single one is dominant over the other
explain multiple alleles
- more than two different alleles exist for the same trait
2. Many possibilities of allele combinations in a population
explain pleiotropy
- Alleles at a single locus may have effects on two or more traits/phenotypic effects
- Example: sickle cell disease
- Mutant allele at beta globin locus has different effects and causes different symptoms
explain epistasis
- nteraction b/w products of gene pairs
* Interaction b/w two genes in which one of the genes modifies the expression of another
what are linked genes
ocated close together on a chromosome , making them likely to be inherited together (left)
diff b/w urine + thymine
o Uracil is missing a methyl group at carbon 5 of the pyrimidine ring
chemical classification of the nitrogenous bases
- Purines:
- Adenine (A),
- thymine (T),
- Pyrimidines
- guanine (G),
- cytosine (C)
how to work out chemical orientation of DNA
- 5’end (five prime end), contains a phosphate group attached to the 5’ carbon of the ribose ring
- 3’end typically unmodified from the ribose -OH substituent
how are bonds b.w stacking dna
van der wall
how is DNA packaged in cell
in form of Chromatin= DNA + histone proteins
diff between euro and heterochromatin
o Euro: less condensed (can be transcribed)
o Hetero: highly condensed
what phase does chromosome replication
s phase
what are the two locations classifications of genes described
cytogenetically or molecularly
explain cytogenetical classification
• Eacharm divided into (cytogenetic bands)
• Counting from the centromere out towards telomeres
• P= petite arm (shorter) p1, p2, p3
Q= queue arm (longer) q1, q2, q3
explain molecular location of a gene
- Sequencing: technique determine nucleotide order on DNA
* Nucleotide sequence can be used to map genes (location) on DNA by counting nucleotides
what does non coding DNA do
biochemical activities, including regulation of gene expression, organisation of chromosome architecture, signals controlling epigenetic inheritance
describe dna replication in prokaryotes
DNA is rearranged as a circular ring chromosome
3. Starts at a specific point DNA= origin of replication
describe dna replication in Eukaryotes
Eukaryotes: DNA is rearranged as discrete chromosomes
• DNA replication happens in nucleus
• Semiconservative DNA replication
• One old parent strand paired with a newly synthesized strand
