mendelian genetics Flashcards
1
Q
briefly describe the early ideas of inheritance
A
- information from each body part passed on independently
- inherited genes can disappear / reappear, segregate into alternative forms, be more likely than others
2
Q
who was gregor mendel
A
- early geneticist, from merinos to plant genetics
- early life: augustinian monastery, studied statistics and probability
- later life: conducted plant breeding experiments (traits from pure-breeding crosses)
3
Q
what was his experimental design
A
- pea plants: 7 traits, each with two distinct and discontinuous forms (easy to control mating)
- allowed pea plants to self-fertilise for several generations, assured constant traits (all had white flowers = true breeding)
- performed crosses between varieties exhibiting alternative character forms (true breeding purple flowers with true breeding white flowers)
- permitted hybrid offspring to self-fertilise for several generations (demonstrate segregation)
4
Q
what is the model of inheritance
A
- parents transmit information about traits called ‘heritable factors’ (genes) to offspring
- each individual receives two factors that may code for all the same or alternative character trait
- not all copies are identical
- two alleles do not influence each other
- presence of allele does not mean it will be expressed
5
Q
what is the modern interpretation of mendel’s results
A
- alleles: alternative forms of a gene (alternative phenotype)
- homozygous: two same alleles
- heterozygous: two different alleles
- genotype: totality of alleles (1:2:1, disguised ratio)
- phenotype: physical appearance (3:1 observed ratio)
- punnett squares: diagram to visualise possible outcomes (probability)
6
Q
what is mendel’s law of hereditary
A
- law of segregation: individuals carry a pair of genes, termed alleles, influence inherited traits, alleles segregate during formation of gametes
- law of independent assortment: genes that are located on different chromosomes assort independently of one another
7
Q
what are the addition / multiplication rules of probability
A
- M: chance of two or more independent events occurring together = probability of each event multiplied together
- A: probability of an event that can occur in more than one way is the sum of the separate probabilities of each way
8
Q
what is a dihybrid cross
A
- cross of parents alleles in order to determine genotype of children
- define the alleles
- define the cross
- define the gametes
- use punnet square
- interpret results
9
Q
what is continuous / polygenic variation
A
- a single phenotypic character is affected by two or more genes
- effect: range of small differences (traits) for one character, skin colour
- one phenotype and more than one gene
10
Q
what are pleiotropic effects
A
- opposite of continuous variation
- one gene / allele is able to affect multiple phenotypic characters
- one gene and more than one phenotype
11
Q
what is incomplete dominance
A
- lack of complete dominance
- heterozygotes are intermediate in colour
- Rr x Rr = RR (red) or Rr (pink) or rr (white)
12
Q
what is epistasis
A
- phenotypic expression of one gene affects that of another (interaction of two alleles / genes)
- effect: gene interferes with expression of another gene
- fur colour (BB / Bb = black or bb = brown) AND pigment deposited on fur
13
Q
what is co-dominance
A
- no single allele is dominant, each allele has its own effect
- separate and distinguishable
- both phenotypes expressed in heterozygotes
14
Q
what are multiple alleles
A
- some genes have more than two alleles
- ABO blood groups
- human gene codes for enzyme (I) which adds carbohydrates to the surface of RBC, 3 possible alleles and each person gets two
15
Q
what are the ABO blood groups
A
- genetics, immunology
- antibodies: produced against foreign blood surface sugars
- type A, produces anti-B antibodies (cannot receive B or AB)
