Weel 12 - Pattern of inheritance Flashcards
1
Q
Allele
A
- A specific version of a gene
- Diff alleles may code for diff forms of same protein → result in different characteristics
2
Q
Law of segregation
A
- Alleles will separate during meiosis
→ Each gamete will receive one allele
3
Q
Models of inheritance: particulate inheritance
A
- offspring are a combination of both parents and that the characteristics of parents are passed on as a separate entities
- parents pass on discrete heritable units (genes) that retain their separate identities in thei r==r children
- particulate inheritance maintains variation; genes w/ diff alleles that are present in each parent are recombined and passed on
4
Q
Gregor Mendel - Reason studying pea plants
A
- Other research showed that pea hybrids could be produced
- many pea varieties were available
- peas are small plants and easy to grow
- peas can self-fertilise or be cross-fertilised
5
Q
Meldel- experimental method
A
- produce TRUE-BREEDING STRAINS for each trait he was studying
- cross-fertilise true breeding strains having alternate forms of a trait → also perform RECIPROCAL CROSSES
- allows hybrid offspring to self fertilise for several gens & count no. of offspring showing each form of the trait
6
Q
monohybrid crosses
A
- cross to study only 2 variations of a single trait
- mendel produced true-breeding pea strains for 7 diff traits
→ flower colour, seed colour, seed texture, pod colour, pod shape, flower position, plant height
7
Q
F1 Gen
A
- first filial gen
- offspring produced by crossing 2 true-breeding strains
- for every trait mendel studied, all F1 plants resembled only 1 parent
→ reffered to this trait as dominant
→ alternative trait was recessive - No plants w/ characteristive immediate betw 2 parents were produced
8
Q
F2 gen
A
- second filial gen
- offspring resulting from the self-fertilisation of F1 plants
- although hidden in the F1 gen, recessive trait had reappeared among some F2 individuals
- counted proportions of traits
→ 3:1
9
Q
3:1 , really 1:2:1
A
F2 plants - 3/4 plants w/ dominant - 1/4 plants w/ recessive -ratio is actually: →1 true-breeding dom plant → 2 not-true-breeding dom plant → 1 true-breeding recessive plant
10
Q
Principles of segregation
A
- parents transmit discrete factors (genes) to their offspring
- each individual receives onecope of a gene from each parent (relates to gametes being haploid)
- Not all copies of gene are identicle
- allenes remain discrete -no blending
- presence of alleles does not guarantee expression
11
Q
Albinisim
A
- cond. : pigment melanin is not produced
- pedigree for form of albinism due to nonfunctional allele of enzyme tyrosinase
- M & F affected equally
- most affected individuals have unaffected parents
12
Q
mendel - extensions
A
- Mendel’s model of inheritance assumes that
→ each trait is controlled by a single gene
→ each gene has only 2 alleles
→clear dom-reces relationship betw alleles
13
Q
multiple alleles
A
- may be more than 2 alleles for a gene in a population
- ABO blood types in humans (3 alleles)
- each individual can only have 2 alleles
- no. of alleles possible for any gene is constrained, but usually more than two alleles exist for any gene in an out breeding population
14
Q
Polygenic inheritance
A
- when multiple genes are involved in controlling the phenotype of a trait
- phenotype is an accumulation of contributions by multiple genes
- traits show continuous variation & referred to as quantitative traits
→ eg. human hright
15
Q
Environmental influence
A
- coat colour in himalayan rabbits and siamese cats
→ allele produces an enzyme that allows pigment production only at temp below 30 degC
