Human Genetics 1 & 2 Flashcards by Keeley McGee

describe dominant allele

mask other traits (Written in capital) (one copy needed)

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describe recessive allele

is covered when dominant is present (Written with lowercase) (two needed)

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what is a purebred

homozygous (two identical alleles e.g. aa, AA, for particular gene)

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what is hybridisation

crossing of two purebred plants

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what are the 3 generations according to mendel

P gen (parental)
F1
F2

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what is a genotype

combination of genes in individual (written underlined or in italics)

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what is a phenotype

physical trait and depend on genotype

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What probabliitys do you include in punnet squares

prob of geno + pheno

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What is mendels first law

law of dominance

- only one trait is shown= dom trait

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what is a dihybrid cross

crossing with two genes/traits e.g. yellow/green + round/wrinkled

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mendels second law

law of segregation
inherited traits exists in alleles
- this pairs segregate + sex cell only receives 1

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mendels third law

law of independent assortment

- alleles distributed indecently from one another

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what are monogenic traits

Traits (genes/alleles) with simple Mendelian inheritance
Characteristic/trait determined by a single gene/allele
One locus on a chromosome

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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?

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when determining mode of inheritence= whats the first step

do all affected individuals have an affected parent
Yes= dom
No= rec

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when determining mode of inheritence= if dom, how to determine whether auto or x linked

father to son transmission
yes= autosomal
no= x linked

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when determining mode of inheritence= if rec, how to determine whether auto or x linked

only males affected?
yes- x linked
no= auto

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if sexes are equally affected in monogenic disease, is it x linked or auto

auto

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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

1. 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