Midterm!!! Flashcards
What is DNA?
Deoxyribonucleic acid
What are genes?
Sequences of DNA that code for RNA and protein
How long is our DNA?
Two meters long
How many chromosomes do we have?
46
How many genes do we have?
about 300,000
Where is meiosis happening now?
In human gonads (males only)
What is chromatin?
DNA and proteins found during interphase
What is a nucleosome?
A basic unit of packaging for DNA
What are histone proteins?
The proteins that DNA always wraps around (even when decondensed). This is the first “level” of DNA packaging.
What is the second level of DNA packaging?
Beads-on-a-string packaging, where nucleosomes are connected to one another.
What is the third level of DNA packaging?
The 30 nm fiber.
What are the two 30 nm models?
The solenoid model and the Zig Zag model.
What is the zig zag model?
The beads-on-a-string zig zag across each other
What is the solenoid model?
The beads-on-a-string form a super coil
What are the fourth and fifth levels of DNA packaging?
The models are unclear, but loops are likely formed.
What’s a karyotype?
A profile of chromosomes.
How are chromosomes in a karyotype arranged?
From largest to smallest.
How are chromosomes in a karyotype matched?
They are paired by size, centromere position, and banding patterns
What is a homologous chromosome?
Two chromosomes that make up a pair (one from mom, one from dad)
What are the characteristics of homologous chromosomes?
They will have the same length, position, and banding patterns, and will both have genes with the same characteristics.
What is the exception to the patterns of homologous chromosomes?
The X and Y chromosomes
What are the sex chromosomes?
The X and Y chromosomes
What are the autosomes?
The other 22 pairs of chromosomes.
What are gametes?
Sperm and egg cells.
How many sets of chromosomes are in gametes?
1 set or 1n (haploid)
What are somatic cells?
Body cells
How many sets of chromosomes are in somatic cells?
2 sets or 2n (diploid)
Why do we perform meiosis?
To halve the number of chromosomes in gametes
What are the gonads in humans?
Testes and Ovaries
How do the gamete cells restore the diploid condition?
Fertilization
What are some advantages of asexual reproduction?
Reproduction is faster, there can be more offspring, they don’t need to spend energy looking for a mate
What are some disadvantages of asexual reproduction?
Lack of variation means an entire population can be wiped out by an environmental change.
What are some advantages of sexual reproduction?
Variation lets the species adapt and survive if the environment changes, less offspring means more time for child rearing
What are some disadvantages of sexual reproduction?
Two parents are needed for sexual reproduction to take place.
When would an asexual lifecycle be favored by evolution?
When the environment is static
When would a sexual lifecycle be favored by evolution?
When the environment is dynamic
In what types of organism does binary fission occur?
Prokaryotes, some single-celled eukaryotes
What type of DNA is found in prokaryotes?
One circular chromosome
What are some differences between mitosis and binary fission?
Binary fission does not go through mitosis (Prophase, Metaphase, Anaphase, Telophase), there is no mitotic spindle, and the DNA will replicate quickly and all throughout its lifecycle
What is the general process of binary fission?
Replication begins at the origin of replication (ori), the two new origins of replication start migrating to the poles, the plasma membrane is synthesized between the DNA and around the cell to elongate it, FTsZ is a protein that forms a ring to help pinch in the cell, and the cell wall forms a septum with the plasma membrane between the new daughter cells.
What is a spore?
The gamete cells for a fungi; haploid and single-celled
What is mycelium?
A mass of thread like proteins; the vegetative part of a fungus, capable of reproduction
What is the Hyphae?
Each individual fibrous strand of mycelium
What is the fungus lifecycle?
• There are two cycles, one asexual and one sexual
• The only thing that fuses at first is the cytoplasm, not the nuclei
◦ Protective layer called ascus
• Four ascospores undergo mitosis to create eight haploid cells
What is true breeding?
When all of the offspring of a parent are the same
What are alleles?
Versions of genes
How do inherited traits get passed down to offspring?
During meiosis, DNA is duplicated and then alleles are separated in a way so that every gamete receives every gene in the body.
What are characteristics?
The genes that a person will inherit
What are traits?
The version of a characteristic
What is a gene?
A segment of DNA that codes for a characteristic in the body
What does it mean to be Homozygous?
All of the alleles for a gene are the same
What does it mean to be Heterozygous?
The alleles for a gene are different
What does it mean to have a dominant allele?
In a heterozygous individual, this trait will be expressed
What does it mean to have a recessive allele?
In a heterozygous individual, this trait will be repressed
Why was it important that Mendel used pea plants in his expiriments?
Each gene he tested for only had two alleles, the pea plants produce a large number of offspring and have a short lifecycle, and he could strictly control the mating process.
Why were the traits that Mendel tested important?
Each allele was found on a different chromosome
What is Medel’s law of Segregation?
Two alleles for a gene will separate in the formation of gametes
What is Medel’s law of Independent Assortment?
The alleles for one gene will separate independently of the alleles for another gene
What is a testcross?
When you cross an individual of unknown dominant genotype with a homozygous recessive individual
What is the purpose of a testcross?
To test whether the individual is homozygous dominant or heterozygous
What is a backcross?
When you mate an F1 generation with the parent generation or another pure breeding plant.
What is the difference between a monohybrid cross and a dihybrid cross?
A monohybrid cross is between two individuals who are heterozygous for one trait, while dihybrid crosses occur between two individuals who are heterozygous for two traits.
What is the ratio of dihybrid cross?
9:3:3:1
How do you calculate the probability of two or more independent events occurring together?
By multiplying their individual probabilities
How do you calculate the probability of any one of two or more mutually exclusive events occurring?
By adding the probability of these events
What does it mean for one allele to be dominant over another?
Dominance means that the trait will be expressed in the phenotype when paired with a recessive allele. The dominant is not more common, and it does not suppress the recessive.
What is a locus?
The location of a gene
How does the genotype result in a phenotype?
The DNA contains the codes for the recipe (RNA) for making proteins in ribosomes. The protein itself is the physical expression of the genotype.
What is complete dominance?
The phenotype of the homozygous dominant and heterozygous are the same.
What is incomplete dominance?
The heterozygous situation expresses a phenotype somewhere in between the homozygous dominant and recessive phenotypes.
What is codominance?
The heterozygous situation has two dominant alleles where both are expressed.
What is pleiotropy?
One gene that has many effects
What are some common examples of pleiotropy?
Phenylketonuria is when a defective gene impacts the enzyme that converts phenylalanine to tyrosine, causing phenylalanine to accumulate in the blood and tissues, which leads to mental retardation, issues with brain development, and jerky movements. Marfan’s syndrome is a disease that effects connective tissue, which leads to long limbs and problems with the heart.
What is epistasis?
One gene affects the expression of another gene.
What is polygenic inheritance?
The additive effect of two or more genes (traits that run on a bell curve)
What situation in a pregnancy would be dangerous for the baby in terms of Rh?
If a mom was Rh- and the baby was Rh+, her antibodies could attack the baby’s blood.
What is the recombination frequency?
The frequency at which new allele combinations are produced
What is the equation for recombination frequency?
The recombination frequency is the number of recombinant progeny divided by the total number of progeny times 100
How do we know if two genes are linked?
If the recombination frequency is less than 50%, the genes are linked
What are linked genes?
Genes that are found on the same chromosome, and that are frequently inherited together
What is recombination?
The sorting of alleles into new combinations
What is the relationship between crossing over and linkage?
Crossing over separates alleles while linkage keeps alleles together
If genes are located closer to each other, what happens to the recombination frequency?
It decreases
What are the map units for genes?
One map unit is equal to a 1% recombination frequency
What does it mean for a gene to be sex linked?
It’s found on either the X or the Y chromosome
Why is crossing over less common with sex chromosomes?
Many parts of the X and Y chromosomes are not homologous
What type of genes are on the sex chromosomes?
The Y chromosome has many male-determining genes, but there are many other genes that aren’t sex related, like eye cone development.
What do we call male genotypes (genes with only one allele) that are neither heterozygous not homozygous?
Hemizygous
What does female DNA do to make up for the extra genetic information females have?
One of the X chromosomes will become inactive (barr body).
What is evolution?
A change in allele frequency across a population
What are the three main components of evolution?
The origin of the variation, the redistribution of the variation, and the sorting of the variation
What is the source of all variation?
Mutations
How is a variation redistributed?
Through the movement of alleles (gene flow) by immigration or emigration, or through recombination
What is the effect of gene flow within a population?
Variation is increased
What is the effect of gene flow between populations?
The two populations will become more similar, which will decrease variation
What is nonrandom mating?
Redistributing variation within a population but above the chromosomal level (like mates with like)
How is variation sorted?
Through genetic drift
What is genetic drift?
Change in allele frequency due to chance (survival of the luckiest)
What is the effect of genetic drift within a population?
The variation will decrease
What is the effect of genetic drift between populations?
The variation will increase
How is genetic drift related to population size?
Genetic drift is more noticeable in smaller populations than in larger.
What is the GREAT HISTORICAL FALLACY?
We’re taught that evolution is adaptive, but it isn’t always because of genetic drift!
What is the difference between genetic drift and natural selection?
Genetic drift is survival of the luckiest while natural selection is survival of the fittest
What are primary forces in evolution?
Components with a major effect on evolution, such as genetic drift, natural selection, and mutation
What are secondary forces in evolution?
Components with a minor effect on evolution, such as nonrandom mating and recombination
What is population genetics?
The study of the change in the gene pool of a population
What is a gene pool?
The total genes in a population
What does a change in a population’s gene pool indicate?
Evolution is occurring
What are the assumptions of the Hardy-Weinberg Principle?
The breeding population is large, mating is random, there is no mutation, there is no migration, and there is no natural selection.
What are the implications of the Hardy-Weinburg Principle?
If all assumptions are true and a population is in Hardy-Weinburg equilibrium, the population is not evolving.
What is the null hypothesis of population genetics?
A population is in Hardy-Weinburg equilibrium
If a population is in Hardy-Weinburg equilibrium, what will the allele frequencies be?
p+q=1
If a population in in Hardy-Weinburg equilibrium, what will the genotype frequencies be?
p^2+2pq+q^2=1
What can the Hardy-Weinburg principles be used for?
Determining allele and genotype frequencies and determining if a population is evolving.
