Genes Flashcards
Genotype =
the alleles present at a given locus
Autosome =
Chromosomes that aren’t the sex chromosomes
Gene =
A sequence of nucleic acids that contribute to the phenotype
Loci =
A location on the chromosome
Phenotype =
The observable characteristics as a result of the genotype
What is the Central Dogma? And who named it?
An explanation of the flow of genetic information in a biological system
DNA —-> RNA —-> Protein
Named by Francis Crick
G x E =
genetic x environmental interaction = effects the phenotype
Pleiotropy =
one gene influences two or more seemingly unrelated phenotypic traits
Polygenic traits =
a trait effected by many genes e.g. height
Processes that don’t fit the central dogma like epigenetic inheritance, don’t fit because…
DNA is still the ‘information’ source but the process is not sequence dependant
sources of change to the genotype:
- mutations
2. recombination of alleles during meiosis
three types of changes to the DNA sequence:
- Base pair substitutions
- Duplication
- Deletion
Base pair substitutions:
transitions =
a change of base; either purine to purine or pyrimidine to pyrimidine
Base pair substitutions:
transversions =
a change in base; either purine to pyrimidine to purine or purine to pyrimidine
Purine bases =
guanine and adenine
Pyrimidine bases =
cytosine and thymine
duplication =
when a base is accidentally duplicated e.g:
CTACG ——> CTAACG
deletion =
when a base is accidentally deleted e.g:
CTGACG ———> CTG_CG
which can be inherited: mutations in the somatic cells or the germline cells?
Only in the germline cells, somatic mutations cannot be passed down
Inversion =
orders of genes at a locus have been swapped with each other
Translocation =
When the end of a chromosome has been copied and pasted onto the end of another, resulting in varying lengths of chromosome pairs
Errors of chromosomal dose can cause…
Conditions such as Down syndrome (trisomy of chromosome 21 occurs as non-disjunction happens during cell division)
females have 2 X chromosomes and males have 1, to equalise the X dose between males and females, what happens?
In females, 1 X chromosome is randomly silenced or inactivated
females are said to be mosaic for inactivated X chromosomes, what does this mean?
In different cells in the body, a different X chromosome may be silenced.
Even though there are more possible transversions than transitions, transitions are more likely to occur, why is this?
substituting a single ring for another single ring or a double ring to another double ring is more likely than substituting single for double or vice versa.
synonymous mutations =
when the base change doesn’t change the amino acid coded for
non-synonymous mutations =
when the base change does change the amino acid coded for
frame shift mutations =
a bases insertion or deletion causes a frameshift and therefore a change in the amino acids coded for.
Mitosis or Meiosis? •Ploidy halved •Produces 4 cells •Homologous chromosomes pair •Recombination between homologues
Meiosis
Mitosis or Meiosis? •Ploidy maintained •Produces 2 cells •Homologues don’t pair •No recombination
Mitosis
Ploidy =
Ploidy is the number of complete sets of chromosomes in a cell
Order of mitosis:
Hint: I Prefer Milk And Tea
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase and cytokinesis
Order of meiosis?
Hint: I Prefer Milk And Tea x2
- Interphase 1 6. Interphase 2
- Prophase 1 7. Prophase 2
- Metaphase 1 8. Metaphase 2
- Anaphase 1 9. Anaphase 2
- Telophase1+cytokinesis 10. Telophase2+cytokinesis
Mitosis or meiosis?
2n -> 4n -> 2n
Mitosis
Mitosis or Meiosis?
2n -> 4n -> 2n -> n
Meiosis
Genetic consequences of meiosis =
- Parental chromosomes are changed
- Different combinations of alleles
- Unique mixture of recombined chromosomes
- After fertilisation, new pairings of chromosomes
Recombination is:
- More likely between physically________ positions
- Very unlikely between very_________ positions
- Less likely at chromosome__________.
Far
Close
Ends
Asexual reproduction: Agametic =
- Budding or fission
* Offspring are genetically identical to the parents
Asexual reproduction: Parthenogenesis =
- Gametes produced by mitosis or a modified meiosis
* Offspring are identical to the parents, and to each other
What equation can we use to calculate genotype frequencies in a population?
Hardy Weinberg Equation:
a² + 2(ab) + b² = 1
In a population of otters (Lutra lutra) in Scotland there are two alleles at a locus of interest. Allele A has a frequency of 0.7 and allele B a frequency of 0.3 What proportion of each genotype would you expect in such a population if it was at Hardy-Weinberg equilibrium?
AA = 0.49 AB = 0.42 BB = 0.09
karyotype =
the complete set of chromosomes of an individual
Synteny =
Conservation of regions of chromosomes between species
Homologue =
genes that share a (hypothesised) common ancestor
Orthologue =
genes that share a common ancestor but have separated with speciation
Paralogue =
descendants of a duplicated gene
Euploid =
A change in the number of complete sets of chromosomes e.g 4n –> 5n
Aneuploid =
change in the number of individual chromosomes e.g
46 —> 47 (Down syndrome)
Autopolyploid =
chromosomes coming from one species
Allopolyploid =
Chromosomes coming from different species
