GENETICS FINAL EXAM

What does a heritability of .8 mean?

80% of the variation we see for that trait in that population is determined by genetic variation.

what are the 3 types of natural selection? visualize the graphs for each, if applicable.

1. directional: eventually results in only the favored genotype.

2. stabilizing: also known as over-dominance. heterozygous is the most fit genotype. it is a normally distributed graph.

3. disruptive: also known as under-dominance. heterozygous is the least fit genotype. it is a unimodal graph.

what does the F stand for in the inbreeding HWE?

the inbreeding coefficient is the likelihood that 2 alleles are from a common ancestor.

polymorphisms

many types of variant alleles, but not one has an advantage over another.

what are the 2 barriers that prevent fertilization? provide examples. what ideology do they protect?

• pre zygotic: the zygote doesn’t even form in the first place. (ex. preferences)

• post zygotic: the zygote forms but it either cannot survive or it is sterile. (ex. the zygote is infertile)

Protects reproductive isolationism

Prevents different species from interbreeding

allopatric vs sympatric speciation

allopatric: physical geographic barrier initiations speciation by blocking gene flow

sympatric: less gene flow in a species not due to geographic barriers (an example is mating preferences)

anagenesis vs cladogenesis

anagenesis: evolution within a species

cladogenesis: the point where one pieces splits into one

homologs vs paralogs vs orthologs

• homologs: related species

• paralogs: homologous sequences in the SAME species. this occurs when genes duplicate and specialize.

• orthologs: only after speciation. the genes evolve separately between 2 separate species. orthologs are the homologous sequences found in DIFFERENT species.

*** make sure u can identify them based on a pic!

what are the 3 checkpoints for cancer?

1. G1/S CHECKPOINT: monitors for proper cell size and undamaged DNA

2. G2/M CHECKPOINT: holds circle until replication and DNA repair are complete (occurs right before mitosis)

3. M CHECKPOINT: ensures proper spindle formation and attachment (happens during mitosis)

tumor suppressor gene vs proto-oncogene

• tumor suppressor gene: prevents bad cells from proliferating, if there’s damaged DNA. acts as the brakes. recessive acting

• proto-oncogene: promotes regular cell division and growth. acts like the gas pedal. dominant acting

two-hit hypothesis VS haploinsufficiency (give example)

• two-hit hypothesis: says that the tumor suppressor genes are recessive acting. both allele in tumor repressors have to be defective in order to cause uncontrolled cell division.

• haploinsufficiency: happens when having just ONE mutated allele becomes problematic. (not recessive)

  • example: bloom syndrome (one mutated allele increases risk of colorectal cancer)

name 3 tumor suppressors, their functions, and their genetic maps if applicable.

1. BRCA1 AND 2: repairs double strand breaks

2. p53: functions at G1, normally stops replication if it detects damaged DNA

   • small DNA damage → p53 → p21 —| cell cycle

   • large DNA damage → p53 → Bc12 → cell death

3. RB: retinoblastoma; RB normally binds to E2F (transcription factor) which stimulates replication

   • RB —| E2F → replication

what’s an example of a proto-oncogene

c-myc

• abnormal proliferation of B-cells causing Burkitt’s Lymphoma (translocation on chromosome 8 and 14)

• abnormal proliferation of STEM cells causing Myelogenous Leukemia (translocation on chromosome 9 and 22)

HOW CAN VIRUSES CAUSE CANCER? what is clonal evolution?

• viruses can infect a cell near a proto-oncogene and its promoter over-expresses the proto-oncogene

• viruses can also mutate and rearrange proto-oncogenes

clonal evolution is evolution that happens within a tumor. most mutations are detrimental to the cell, but the ones that live will proliferate and form a malignant cell

HOW CAN DNA REPAIR MECHANISM DEFECTS CAUSE CANCER? (name 3)

1. defective nucleotide excision repairs: skin cancer (ex. UV exposure and Xeroderma pigmentosum)

2. defective mismatch repair: base mismatches (ex. colorectal and stomach cancer)

3. defective double strand break repair: (ex, muted BRCA 1 and 2)

HOW CAN TELOMERE LENGTH CAUSE CANCER?

when a cell becomes too short, it is normally supposed to die. sometimes the cell can mutate so that even if its too short, it will still proliferate. this is why cancer cells often show abnormally telomerase activity.

HOW CAN VASCULARIZATION CAUSE CANCER?

ANGIOGENESIS!!!! when blood vessels attach to the tumor, so the cancer metastasizes.

PCR 3 steps

denature, anneal, extend

broad sense variability vs narrow sense variability

broad sense variability: H squared→ proportion of phenotype variance due to a genetic effect

narrow sense variability: h squared→ promotion of phenotype variance due to additive genetic effects

explain the different MZ:DZ ratios

• high MZ: low DZ → genetic effects

• equal MZ: DZ → environmental effects

• low MZ (but still higher than DZ) → both genetic and environmental

Explain the role of restriction enzymes, DNA ligase, vectors and host cells in DNA recombinant technology.

• Restriction enzymes cut DNA at specific sequences.

• DNA ligase joins DNA fragments.

• Vectors (like plasmids) carry foreign DNA into host cells.

• Host cells (usually bacteria) take up the recombinant DNA and replicate it, producing clones

explain southern vs northern vs western blots. which one is used for the golden rice genome?

• southern (used for golden rice)- DNA is separated

• northern- RNA is separated

• western- proteins are separated

Forward vs. Reverse Genetics

give examples of Technologies Used in Reverse Genetics

• Forward: starts with phenotype → finds gene.

• Reverse: starts with gene → alters it to observe phenotype

  • RNAi, CRISPR, gene knockout, transgenic mice, and microarrays

advantages and disadvantages of clone-by-clone sequencing and whole-genome sequencing

Clone-by-Clone vs. Whole-Genome Sequencing

• Clone-by-clone: map first, then sequence (accurate but slow).

• Whole-genome shotgun: random sequencing and assembly (fast but computationally complex)

define SNPs and SNP Haplotypes

• SNP: single nucleotide variant present in ≥1% of population.

• Haplotype: group of SNPs inherited together on the same chromosome

explain the golden rice thing. explain how cDNA is made and what its used for. also explain the diff components of an expression vector. Lastly, describe the Ti plasmid and how it is used to create transgenic plants.

rice is a staple food in asia, but they have alot of vitamin a deficiencies because rice doesn’t have vitamin a. Scientists engineered rice to make vitamin A by: Adding two genes: One from a daffodil or maize (called PSY). One from a bacterium (called CRTI). These genes tell the rice cells how to make beta-carotene (what makes carrots orange and turns into vitamin A in our body). They take these genes and make cDNA so they only have the important parts. cDNA takes mRNA and uses reverse transcriptase to make cDNA, which only includes the useful exons. Expression vectors are what transport the cDNA into the new cell. The Ti plasmid is a bacteria that inserts its DNA into cells. It is used to transfer the gene into the rice’s genome because it's a natural way to insert genes in plants.