genetics exam 1 + 2 culmulative

1. What are the roles of DICER and RISC and what system do they occur?

- DICER cleaves dsRNA into fragments (miRNA + siRNA) - RISC combines fragments, removes one of dsRNA - occurs in RNAi mechanism

1. What are the two repair systems for DSBs?

- NHEJ (nonhomologous end joining) - SDSA (synthesis-dependent strand annealing)

1. What is the role for tRNAs in translation? How do they become charged?

- adaptor molecules that interpret and act on information carried in mRNA - have anticodon sequences complementary to mRNA codons - aminoacyl tRNA synthetase binds the AMP-amino acid to a tRNA molecule, releasing AMP and attaching the amino acid to the tRNA

1. What is an inversion and are there any consequences? Know the difference between the 2 types and what the result product is (what type of chromosome will be at the end)?

- balanced rearrangements/no change to amt of genetic material - paracentric = centromere outside of inverted region (crossing over makes dicentric chromosome -> dicentric bridge and breaks, missing genetic material) - pericentric = centromere inside of inverted region (crossing over makes duplicated and deleted regions of products (two normal + two abnormal gametes)

1. What type of testing determines if a person is a heterozygous carrier for a recessive disease? If one partner is determined to not be a genetic carrier does the other partner need to be tested?

- carrier genetic testing - no

ZOO-FISH description

- comparative chromosome painting - uses whole chromosome to delimit homologous segments *remember strands of chromosomes w/ a few being a diff color

g-banding description

- differential staining along chromosome length

1. Slippage is caused by the dissociation of what during replication? This can lead to what kind of disorders?

- dissociation of DNA polymerase - causes small insertions/deletions - causes trinucleotide repeat expansion disorders (i.e. Huntington disease)

1. How does sister chromatid exchange occur? Can SCE lead to mutations?

- double stranded breaks during S phase of mitosis - caused by chemicals, UV, mutations - yes, Bloom's syndrome

1. What is chromosomal nondisjunction and how does it affect ploidy?

- failure of chromosomes/sister chromatids to separate during cell division - make aneuploid cells (unequal sets of chromosomes)

FISH description

- fluorescent in situ hybridization - probes emit fluorescent light *remember colorful chromosomes

1. Fetal cell sorting is done by and can identify which diseases? (see 2 listed)

- identifies/isolates fetal cells in maternal blood for analysis - cystic fibrosis + spinal muscular atrophy

1. What does it mean to be isoaccepting and how does it apply to the wobble hypothesis?

- isoaccepting = tRNA molecules with different anticodons for the same amino acids - hypothesis = predicts that hydrogen bonding between the anticodon at the third codon position is subject to modified base-pairing rules - relaxation of complementary base pairing at the third position of a codon can reduce the number of different tRNAs required during translation

1. What is a deletion and what are the consequences of this aberration?

- loss of part of one chromosome arm - loss of chromosome segments, gene products, changes in phenotypes

c-banding description

- only centromeres are stained

1. What is a point mutation? Define missense, nonsense and silent (synonymous) mutation.

- point: change in one base pair in DNA molecule - missense: changes one amino acid - nonsense: creates premature stop codon - silent/synonymous: no AA sequence change

1. Differentiate between the 3 reversion mutations.

- promoter: altering nucleotides of promoters - splicing: altering nucleotides of specific sequences at end of intron - cryptic splicing: base-pair substitution makes new splice sites

1. Where does translation occur in the cell and what does it require? (slide 8)

- protein synthesis - ribosomes in the cytoplasm - AAs, mRNA, tRNA, ribosomes

1. What are Okazaki fragments and how are they combined after being synthesized? Know enzyme involved and what strand they are located on.

- short segments of newly synthesized DNA that are part of a lagging strand and is ligated to other Okazaki fragments to complete lagging strand synthesis -Okazaki fragments are combined via DNA ligase

1. What are the 4 different mutation categories?

- spontaneous: natural/random - induced: influenced by external factor - somatic: all cells except germ cells, not heritable - germ-line: only gametes, are inherited

1. What are the two base-pair mutations?

- transition: purine replaces purine/vice versa - transversion: purine replaces pyrimidine/ vice versa

1. Know the 2 bacterial promoter consensus sequences and the 2 forms of termination. (Inverted repeats vs. rut site)

-35 sequence & -10 sequence (pribnow box) intrinsic termination: includes inverted repeat rho-dependent termination: have rut site

1. What is the main function of the small ribosome subunit?

40S - binds mRNA and determines the accuracy of translation of the mRNA codon/tRNA anticodon

how many stages of Prophase I are there? what happens in Pachynema and Diplonema?

5 stages pachynema: start of crossing over diplonema: crossing over is done, creation of tetrad

1. What is the main function of the large ribosome subunit?

60S - protein synthesis/peptide bond formation

what is the ideal phenotypic ratio of the F2 generation in a dihybrid cross? what happens to the ratio for a test cross with a heterozygous individual?

9:3:3:1 2:2 (50% dominant, 50% recessive)

nitrogenous bases in DNA

A, G, C, T

nitrogenous bases in RNA

A, G, C, U

be able to identify monohybrid patterns by Mendel for genotype and phenotype

AA x aa = 4 Aa AA x Aa = 2 AA + 2 Aa Aa x Aa = 1 AA, 2 Aa, 1 aa Aa x aa = 2 Aa + 2 aa

1. **A missense mutation in this gene leads to the size of the Shetland pony.

ACAN

DNA molecule amounts in different stages

G1 = 8 G2 = 16 mitosis = 8 meiosis = 4

1. Highly expressed _________ protein enhances genes and promotes alternative splicing with exon 9 exclusion and exon 10 retention.***

MYC

1. True/False: A two point linkage map most effective way to build genetic maps?

NO (three point linkage map is)

1. PCR amplification and dye terminator sequencing similarities and differences.

PCR: doubles the number of copies of the targeted DNA sequence each cycle Dye terminator: DNA polymerase is used with fluorescent nucleotides to generate new DNA sequences that can be read by a laser and advanced imaging both used to observe DNA segments

1. What are the main components needed for initiation of translation in prokaryotes? Eukaryotes? How do they differ (main points)?

Prokaryotes -mRNA, small subunit, large subunit, initiator tRNA, protein factors, and GTP. Eukaryotes: -eIF, eukaryotic initiation factors, 1, 1A, 3, 5, small subunit, tRNA

1. What is needed to make the RNA polymerase holoenzyme?

RNA polymerase core enzyme + sigma subunit

1. What makes a repressible system? Slide 8

abundance of end product in environment causing gene expression repression

1. In amino acids the N-terminal region of the histone tails can be covalently modified by what 3 mechanisms?

acetylation, methylation, phosphorylation

Define synteny.

all loci on one chromosome are syntenic, regardless of their proximity or interactions in meiosis

test crosses

crosses to determine unknown genotype

1. Cancer cells are _________, meaning they look and behave more like ________ cells.

dedifferentiated, primordial

1. Name the main categories of structural aberrations that can occur in mammalian chromosomes.

deletion, insertion, inversion, translocation

what is DNA

deoxyribonucleic acid carrier of genetic information double-helixed

During the G1 phase, the cell checks for DNA damages that might have occurred during mitosis.

false (G2 does)

how many nitrogenous bases are there?

five

1. **How can XIST be used in a trisomy 21 case?

forms a Barr body to limit expression of X-linked genes

what are homologous pairs?

found in sexually reproducing organisms each chromosome has one carry genes for same trait

1. What is RNA priming?

initiation of DNA replication

1. What are the 3 phases of translation?

initiation, elongation, termination

know the difference between sex linked, sex limited and sex influenced traits?

linked = traits carried in either the X or the Y chromosome limited = expression of a specific phenotype is absolutely limited to one sex influenced = sex of an individual influences the expression of a phenotype that is not limited to one sex or the other

1. What is metastasis?

malignant tumor can invade normal tissues and travel to new locations, forming new tumors

1. What is the main cellular/biological event on which a linkage map depends?

meiosis / meiotic recombination (crossing over)

what is mRNA?

messenger RNA

mitosis v. meiosis

mitosis: - creates 2 identical cells w/ same # of chromosomes as parent meiosis: - reduces genetic info by half

monad vs dyad vs tetrad

monad = single chromosome w/ 1 DNA molecule dyad = replicated chromosome w/ 2 DNA molecules tetrad = two homologous pairs combined together w/ 4 DNA molecules

1. Understand similarities and differences between mutations and DNA sequence polymorphisms.

mutations: <1%, causes disease or are neutral polymorphism: >1%, usually neutral

components of nucleotides

nitrogenous base, sugar, phosphate group

1. What are tumor suppressor genes?

normal genes that function largely at cell cycle checkpoints to pause it until conditions are right to continue

1. What part of the cell does transcription occur?

nucleus

1. How does the mechanism of negative control in the Lac-operon model work in the presence and absence of lactose?

presence: lactose binds to repressor, operator is open, transcription occurs absence: repressor binds to operator, no transcription

Proceeding from the Chromosome Theory of Inheritance, which were the two main candidate molecules for the genetic material?

protein nucleic acids

replicate crosses

repeated crosses involving parents with the same genotypes and phenotypes

what is RNA?

ribonucleic acid

reciprocal crosses

same genotypes are crossed but sexes are reversed

parts of chromosome

sister chromatids connected by telomere p arm = short q arm = long telomeres at ends

submeta vs meta vs telo vs acrocentric chromosomes

submeta = p little shorter than q meta = centromere in center telo = p very short acro = no p arm

1. Define linkage.

the proximity of two or more genes on a chromosome

what is genetics

the study of heredity and the variation of inherited characteristics

1. Post-transcriptional regulation is the second most common regulation.***

true

1. T/F Mutations in the DNMT3A gene occur early in certain leukemias; normally, its product helps methylate chromatin for gene silencing.***

true

Between the interphase and mitosis, cells can enter a stage called G0, in which they are quiescent.

true

DNA synthesis occurs during the S phase of the interphase stage.

true

the transitions from one interphase stage to the other are controlled by cell cycle checkpoints.

true

The interphase is characterized by the absence of visible chromosomes.

true (formed in prophase)

1. What is an inducible operon system?

turned on only when an inducer compound is available

what are genes?

units of inheritance

1. Why is the Tryptophan operon considered a repressible system? How does it differ from the Lac-operon?

when present, causes no transcription to occur (differs from lac operon where its presence made transcription possible)

1. Is the newborn genetic screening mandated in all 50 US States?

yes

1. Review 3-point linkage mapping and how to determine parental, SCO, and DCO gametes and what the possible order could be. Be able to determine probability/gamete frequencies of each given m.u.

-Type the highest observed number of gametes=parental type (no crossing over occurs between the genes) -SCOs are the second most frequent, DCO's are the least frequent (because it requires both crossover events) -Steps to determine order 1.) determine the parentals and DCO type gametes 2.) compare parental and DCO to determine which gene is in the middle 3.) with the determined middle gene, perform SCO between the parentals (with the determined middle gene)

1. List the 3 types of post-transcriptional processing. Once this occurs this allows what to move out into the cytosol? (pre-mRNA v. mature mRNA)

1. 5 capping 2. 3 polyadenylation 3. Intron splicing the initial eukaryotic gene mRNA is called pre-mRNA, fully processed mRNA is called mature mRNA (done in nucleus)

1. Know the 3 eukaryotic promoter consensus sequences.

1. GC-rich box: 5′-GGGCGG-3′ (-90) 2. CAAT box: 5'-CAAT-3' (-80) 3. TATA box: 5′-TATAAA-3′ (-25)

1. Know the 3 types or RNA Pol and what they transcribe for.

1. Pol I: transcribes all rRNA genes EXCEPT for the 5S rRNA 2. Pol II: transcribes all structural genes (all mRNAs) 3. Pol III: transcribes all tRNA genes (nonstructural) + 5S rRNA gene

1. Know the steps of translation. (slide 10 and 11)

1. Ribosome (large + small subunits) holds a strand of mRNA so that its codons align with the docking sites on the large subunit. 2. Incoming tRNA is charged, and it carries abound amino acid to the A site in the large subunit 3. Once docked, it aligns its anticodons with the codons on the mRNA strand and moves to the P site 4. Attaches the newly synthesized amino acid to the forming polypeptide. 5. tRNA exits the ribosome at the E site and is no longer charged.

1. What are the 2 major mechanisms of epigenetic changes?

1. methylation 2. histone modification/chromatin remodeling

1. What are the two types and know differences of prokaryotic gene regulation?

1. negative control: repressor binds + prevents transcription 2. positive control: activator binds + initiating transcription

1. Know the steps of DNA replication in their correct order and know the basics for each step.

1. unwinding and stabilizing of DNA helix - DNA topoisomerase temporarily relaxes supercoiling - helicase breaks H+ bonds between N bases/makes 2 template strands - single-stranded binding (SSB) protein prevent reannealing of separated strands 2. Initiation of DNA synthesis, synthesis of RNA primers - DNA primase synthesizes RNA primers onto existing DNA strands 3. Continuous DNA synthesis-leading strand - DNA pol 3 synthesizes daughter strands and elongates by adding new complementary nucleotides to the 3' OH end of RNA primer - same direction as the movement of the replication fork 4. Discontinuous DNA synthesis-lagging strand - DNA pol 3 extends primer by adding new nucleotides; stops each time when it encounters the previously formed fragment 5. Proofreading and correction errors - DNA pol 1 removes the RNA primers with 5' to 3' exonuclease activity and replaces RNA nucleotides with DNA - DNA ligase joins DNA segments - replication stops when it reaches stop codon - DNA pol 3 proofreads the nucleotides being added and if a nucleotide has been incorrectly added, it recognizes the error, removes the incorrect base, adds the correct nucleotide, and continues on

1. Name one of the genes linked to increased susceptibility to breast and ovarian cancers.

BRCA1

be able to match the nm fibers to structures/terms. Define chromosome scaffold and what its function is and its nm fiber length

DNA - 2nm nucleosomes - 6x11 nm solenoid - 30nm chromatin fiber - 300nm chromatid - 700nm chromosome - 1400nm chromosome scaffold - gives chromosome shape

1. What is the chemical structure differences between RNA and DNA?

DNA - double helix, built with nitrogenous base, pentose sugar (H+ on 2' carbon), phosphate group, AT/GC RNA - OH- on 2' carbon, AU/GC

be able to identify patterns of inheritance from pedigrees discussed in class.

autosomal recessive: - recessive gene found in m & f - can skip a generation (parents may not show it but children will) autosomal dominant: - dominant gene found in m & f - anyone affected will pass it down and affect offspring x linked dominant: - affected MALES = affected daughters (no affected sons) - carrier FEMALES = m/f equally affected x linked recessive: - more affected males than females (color blindness) y linked: - only from fathers to sons cytoplasmic inheritance: - from mother not father

1. Binding of which complex allows for the cooperative binding and increases the ability of RNA polymerase to transcribe the lac operon?

cAMP

what are chromosomes?

carriers of genes

1. Know CODON and ANTICODON. What strand/component are they located on?

codon: located on mRNA, complimentary to DNA anticodon: located on tRNA, complimentary to mRNA