Week 1 Sept 9 Flashcards
Define microevolution. Are these processes repeatable and reversible, or creative and unique?
Individuals and populations (species and below) over a generational time scale (repeatable and reversible)
Define macroevolution. Are these processes repeatable and reversible, or creative and unique?
Species level and above over an evolutionary time scale (creative and unique)
A phylogenetic tree shows __________.
Relationships over time (common ancestors are not living, today)
If the time for life on earth were compared to height of the CN tower in Toronto, then humans would measure only ________
Around 1cm
What is denoted as the common ancestor for the homo genus?
Homo ergaster
Diploid
2n or copies of a genome
Haploid
N or one genome
Genome divided into
Chromosomal pieces
________ chromosomes = haploid
23
______ chromosomes = diploid
46
What happens in sexual dimorphism and reproduction?
Haploid gamete cells join to reproduce a diploid cell
Each human _________ is a single linear DNA molecule with a string of nucleotides that spell out _________ and other information
- chromosome
- genes
The total DNA in all the chromosomes of an organism is its _________
Genome
True or False?
A complete genome is nearly always found in every cell
True
Humans have 46 chromosomes that are in 23 pairs within ____________
A cell’s nucleus
What are pairs of chromosomes called?
Homologous chromosomes
What are autosomes?
The 22 pairs of chromosomes that control traits that do not relate to the gender of an individual
What are sex chromosomes?
The 1 pair of chromosomes that contains the genes that establish gender or sexual dimorphism
What are somatic cells? Are they diploid or haploid?
Body cells have 46 (2N) = diploid
What are germ cells? Are they diploid or haploid?
Sex cells or gametes have 23 (N) = haploid
Paternal gamete = _______
Sperm
Maternal gamete = ________
Ovum
True or False?
Mitochrondria have their own genome
True (mtDNA)
True or False?
Sperm contribute to mitochrondria
False
True or False?
Genes on the X chromosome determines the male sex
False (the Y chromosome)
True or False?
The Y chromosome lacks many genes normally found on the X chromosome
True (the Y chromosome is much smaller than the X chromosome and therefore lacks many genes compared to the X chromosome)
Mitosis
- Growth and repair of cells
- Occurs in body cells
- 1 division
- Results in 2 diploid genetically identical cells
Meiosis
- Formation of gametes
- Occurs in germ cells
- 2 divisions
- Results in 4 haploid genetically different cells
How many potential combinations of chromosomes does meiosis provide?
Maternal and paternal chromosomes get shuffled - 2^23 = 8,388,608 potential combinations
Meiosis provides 2 routes for increasing __________ in the next generation: __________ and ____________
- Variation
- Independent assortment
- Crossing-over
Define genotype
Specific allele combination that is related to a particular trait (or set of traits)
Define homozygous
Diploid state carrying 2 identical alleles at a particular gene or locus
Define heterozygous
Diploid state carrying 2 different alleles at a particular gene or locus
Define phenotype
The physical or outward expression of the genotype, aka a trait
Define mutation
Any heritable change in DNA sequence (excluding meiosis recombination)
Define alleles
Alternate forms of a specific gene or locus
Define dominant allele
A gene version that displays its phenotype when present as only 1 copy as in a heterozygote
Define recessive allele
A gene version displays its phenotype only when present as 2 copies as in a homozygote
Define wild type allele
A way to refer to a ‘normal’ allele or one not associated with a defect or disease trait
Define rare allele
Typically, a frequency of <0.005%
Define codominant or semidominant
Diploid with both alleles contributing to trait
Define hemizygous
Diploid with only 1 allele (e.g. all male X chromosome alleles)
Define haploinsufficiency
A situation where a single wild type allele is insufficient for normal function
Define penetrance
The frequency with which a particular allele or genotype manifests a trait
Define expressivity
The extent or magnitude of an expressed trait with a particular allele/genotype
Define polygenic
Multiple genes contribute to a phenotype or trait
Define pleiotropic
A single gene contributes to multiple traist
Define sex linked
Traits that are determined by genes on the X or Y chromosome
What are 4 evolutionary forces that cause change over time?
- Mutation (because of deletions/insertions in genome)
- Natural selection (more fit = reproduce)
- Genetic drift
- Gene flow (immigration, new alleles to new places)
What are 4 types of mutations? (Big to small)
- Whole chromosomes - aneuploidy (gain or loss = trisomy or monosomy)
- Chromosome segments (inversions, translocations)
- Insertions/deletions
- Substitutions (typically confined to a change in a single bp)
Define single nucleotide polymorphism (SNP)
Mutation of a single nucleotide or bp (can be substitution or indel)
Define transition
Purine to purine and pyrimidine to pyrimidine
Define transversion
Purine to pyrimidine and vice versa
Define missense or non-synonymous
Substitution that alters amino acid coding
Define synonymous
Substitution that does not alter amino acid coding
Define nonsense
Substitution that introduces stop codon and truncates protein
Define frameshift
Indel that results in a change in the reading frame (code is shifted)
Define neutral
A mutation that does not obviously affect fitness or produce a phenotypic trait (selection forces do not apply to such mutations)
What are the pyrimidines?
CT (very close in structure)
What are the purines?
GA (very close in structure)
The effect of natural selection depends on: ___________
Whether a trait is favoured in a particular local environment and it is easily modelled
If we have 2 alleles (different version of gene), A and a, if the frequency of A is 1, what is the frequency of a?
0 (frequency must add to 1)
Define balancing selection
This is a form of selection where the heterozygote is the most fit, which leads to a balance in allele frequencies (although AA is more fit than aa, it does not replace it - the final frequencies represent a balance)
What are 2 key points of genetic drift?
- It’s by chance
- It’s faster in a small population (think of grabbing handful of smarties from large bowl and small bowl)
Define genetic drift
The random chance in allele frequency from one generation to the next because of the basic probability (allele frequency may increase, decrease, or stay the same as a result of chance events during reproduction)
When does gene flow occur?
When an individual from one population moves into another population
2 major effects of gene flow on allele frequency
- New genes can be introduced into a population
- Gene flow between a pair of populations makes them increasingly more genetically similar over time because of the mixing of genes
True or False?
The word population usually refers to the number of the entire species
False (it does not usually refer to the number of the entire species)
What are 2 assumptions regarding mathematical modelling for population genetics?
- Random mating
- Non-overlapping generations
True or False?
In sexual organisms, genotypes (2N) are transmitted from generation to generation
False (rather, alleles are transferred through haploid gametes (N): oocytes and sperm)
Mating pairs mate at the same frequencies as __________
Random collisions between genotypes
Non-random mating is also called __________
Assortative mating
True or False?
1 breeding generation is present at any time
True
