Genetics - Molecules to cells

What is a nucleosome?

(a) DNA wrapped twice around a histone core (b) RNA–protein complex (c) Mitochondrial DNA cluster (d) DNA around polymerase (e) DNA wrapped around non-histone proteins

a

What chromosome regions have higher CG content?

(a) Dark-staining regions (b) Centromeres (c) Satellite DNA (d) Lighter-staining regions (e) Telomeres

d

Epigenetic regulation refers to what?

(a) Viral transformation (b) Heritable expression changes without sequence changes (c) Alternative splicing (d) Gene duplication (e) Chromosomal condensation

b

Proteomics is the study of:

(a) All gene sequences (b) Post-transcriptional mRNA steps (c) All proteins in a cell (d) Ribosomal assembly (e) Transcription factor networks

c

A single-gene defect causing disease is a:

(a) Chromosomal disorder (b) Epistatic interaction (c) Polygenic trait (d) Multifactorial trait (e) Mendelian disorder

e

Achondroplasia involves mutation in:

(a) CYP2D6 (b) HBB (c) FGFR3 (d) Rhodopsin (e) BRCA1

c

Achondroplasia follows which inheritance?

(a) X-linked recessive (b) Autosomal dominant (c) Polygenic (d) Autosomal recessive (e) Codominant

b

An affected X-linked recessive male passes the allele to:

(a) All daughters (b) All sons (c) Half of daughters (d) No daughters (e) Half of sons

a

Carrier females for an X-linked recessive disorder have affected sons at:

(a) 25% (b) 50% (c) 75% (d) 100% (e) 0%

b

Cystic fibrosis inheritance pattern:

(a) X-linked (b) Autosomal recessive (c) Autosomal dominant (d) Mitochondrial (e) Multifactorial

b

CYP2D6 metabolizes:

(a) Codeine (b) Aspirin (c) Ibuprofen (d) Warfarin (e) Acetaminophen

a

Mendel’s third law is the law of:

(a) Segregation (b) Independent assortment (c) Dominance (d) Linkage (e) Epistasis

b

BRCA1/2 mutations increase risk of:

(a) Thyroid cancer (b) Breast cancer (c) Brain tumors (d) Liver cancer (e) Esophageal cancer

b

Meiosis I separates:

(a) Homologous chromosomes (b) Sister chromatids (c) DNA strands (d) Ribosomes (e) Centrosomes

a

Crossing-over occurs during:

(a) Mitosis (b) DNA repair (c) Meiosis II (d) Meiosis I (e) Cytokinesis

d

Chiasmata represent:

(a) RNA splicing sites (b) Recombination points (c) Transcription start sites (d) Helicase binding regions (e) Telomere fusions

b

Dihybrid ratio under independent assortment:

(a) 1:2:1 (b) 9:3:3:1 (c) 3:1 (d) 2:1 (e) 1:1

b

Linked genes show:

(a) No recombination ever (b) Reduced recombination frequency (c) Increased mutation rate (d) Random assortment (e) Identical expression

b

Women are mosaics for X-linked traits due to:

(a) X-inactivation (b) Y-inactivation (c) Chromosomal duplication (d) Pleiotropy (e) Variable penetrance

a

Recombination frequency increases with:

(a) Chromosome thickness (b) Gene silencing (c) Closer spacing (d) Greater distance (e) Higher protein levels

d

Mosaicism results from:

(a) Meiotic nondisjunction (b) Two genetically distinct cell populations (c) Chromosome translocation (d) RNA editing (e) Telomere repair

b

Histone tails regulate:

(a) Ribosome binding (b) Chromatin structure (c) mRNA export (d) tRNA charging (e) Spindle formation

b

Euchromatin is:

(a) Silent chromatin (b) Loosely packed and active (c) Found only in sperm (d) Centromeric DNA (e) Telomeric only

b

Epigenetics studies:

(a) Mutations (b) Chromosome number (c) Heritable expression without sequence change (d) RNA editing (e) Replication speed

c

Continuous variation reflects:

(a) Monogenic traits (b) Polygenic traits (c) Chromosomal traits (d) Mitochondrial traits (e) Linked traits

b

Epistasis is:

(a) Deamination (b) Gene masking another gene (c) Chromatin compaction (d) DNA repair (e) Enzyme misfolding

b

Heritability measures:

(a) Mutation rate (b) Proportion of variation due to genes (c) Phenotype only (d) RNA abundance (e) Dominance strength

b

Phosphodiester bonds link:

(a) Amino acids (b) Bases to bases (c) Sugar–phosphate backbone (d) Proteins to RNA (e) Ribose to adenine

c

DNA replication is:

(a) Conservative (b) Semiconservative (c) Dispersive (d) Non-templated (e) Circular only

b

Helicase:

(a) Unwinds DNA (b) Adds nucleotides (c) Cuts introns (d) Ligates fragments (e) Proofreads DNA

a

DNA Pol I removes:

(a) Introns (b) RNA primers (c) Exons (d) tRNA (e) mRNA caps

b

Most abundant RNA:

(a) mRNA (b) tRNA (c) rRNA (d) snRNA (e) miRNA

c

miRNA function:

(a) Gene silencing (b) Translation elongation (c) DNA replication (d) Chromosome separation (e) Ribosome assembly

a

Prokaryotic promoters:

(a) Bind RNA polymerase (b) Bind ribosomes (c) Silence DNA (d) Remove introns (e) Ligate fragments

a

TATA box is located in:

(a) rRNA genes (b) Enhancers (c) Eukaryotic promoters (d) Telomeres (e) tRNA

c

Introns removed by:

(a) Primase (b) Spliceosome (c) DNAP (d) Ribosome (e) Actin

b

Lac operon inducer:

(a) Glucose (b) Repressor (c) Lactose (d) Galactose (e) IPTG

c

Lac repressor binds to:

(a) Enhancer (b) Operator (c) Ribosome (d) Introns (e) tRNA

b

Translation start codon:

(a) UGA (b) AGG (c) AUG (d) UAA (e) CCA

c

Ribosome A site binds:

(a) Empty tRNA (b) Release factor (c) Aminoacyl-tRNA (d) Initiator tRNA only (e) Helicase

c

Polysomes are:

(a) RNA splicing units (b) Proteasomes (c) Many ribosomes on one mRNA (d) Ribosome precursors (e) tRNA clusters

c

Mismatch repair detects new strand by:

(a) Methylation absence (b) Histone marks (c) RNA primers (d) Ribosome binding (e) Base pairing strength

a

UV light causes:

(a) Frameshifts (b) Deamination (c) Thymine dimers (d) G→A transitions (e) RNA editing

c

Sickle cell mutation type:

(a) Nonsense (b) Silent (c) Missense (d) Frameshift (e) Splice-site deletion

c

Genetic code degeneracy means:

(a) Codons overlap (b) Multiple codons encode same amino acid (c) mRNA unstable (d) tRNA not required (e) Codons vary in length

b

Translation termination requires:

(a) Primase (b) DNA ligase (c) Release factor (d) Helicase (e) Telomerase

c

Which nucleotide base pairs with adenine in RNA?

(a) Thymine (b) Uracil (c) Guanine (d) Cytosine (e) Inosine

b

Which enzyme synthesizes DNA in the 5’ → 3’ direction?

(a) RNA polymerase (b) Helicase (c) DNA polymerase (d) Ligase (e) Primase

c

Which chromatin state is tightly packed and transcriptionally inactive?

(a) Euchromatin (b) Open chromatin (c) Heterochromatin (d) Acetylated DNA (e) Replisome

c

Which process creates new allele combinations on the same chromosome?

(a) Transcription (b) Independent assortment (c) Crossing over (d) Translation (e) DNA methylation

c

What does Chargaff’s rule state?

(a) A=T and G=C (b) A=G (c) C=T (d) A=C (e) Purines > pyrimidines

a

Which bond holds adjacent nucleotides in a DNA strand?

(a) Hydrogen bond (b) Ionic bond (c) Phosphodiester bond (d) Peptide bond (e) Disulfide bond

c

Which enzyme prevents overwinding during replication?

(a) Ligase (b) Primase (c) Topoisomerase (d) Telomerase (e) DNase

c

What stabilizes single-stranded DNA during replication?

(a) Polymerase (b) Helicase (c) SSB proteins (d) Ligase (e) tRNA

c

Differences between Eukaryotic and Prokaryotic transcription

1.      Transcription exclusively in the nucleus

2.      DNA wrapped in histones to give chromatin

3.      Chromatin to be in open configuration for RNAP access

4.      Different RNAP types

RNA I -> rRNA
RNA II -> mRNA

RNA III -> tRNA

Plants have IV and V for gene silencing

5.      Gene structure more complicated, coding structure interrupted by introns

6.      Promoters often have many upstream control elements (enhancers) that bind transcription factors

7.      RNA polymerase II associates with different regulatory proteins e.g transcription factors

Which sequence signals where transcription begins?

(a) Terminator (b) Enhancer (c) Promoter (d) Silencer (e) Origin

c

Which protein binds enhancers?

(a) Repressors (b) Initiation factors (c) Activators (d) Helicase (e) Ligase

c

Which RNA polymerase transcribes rRNA (most)?

(a) RNAP II (b) RNAP III (c) RNAP I (d) RNAP IV (e) RNAP V

c

Which RNA polymerase transcribes tRNA?

(a) RNAP I (b) RNAP II (c) RNAP III (d) RNAP IV (e) RNAP V

c

Which modification protects mRNA from degradation?

(a) Poly-U tail (b) Splicing (c) 5’ cap (d) Base excision (e) Endonuclease removal

c

Which modification increases mRNA stability?

(a) Promoter binding (b) Poly-A tail (c) UTR shortening (d) RNA editing (e) Recombination

b

The P site of the ribosome holds:

(a) Aminoacyl-tRNA only (b) Release factor (c) Peptidyl-tRNA (d) Empty tRNA (e) mRNA cap

c

Which codon always starts translation?

(a) UAA (b) CUG (c) AUG (d) AGG (e) UAG

c

Which enzyme charges tRNAs?

(a) Ribosome (b) Helicase (c) Aminoacyl-tRNA synthetase (d) Ligase (e) Telomerase

c

Which ribosomal site binds incoming aminoacyl-tRNA?

(a) P site (b) E site (c) A site (d) T site (e) R site

c

Which mutation changes one amino acid to another?

(a) Nonsense (b) Frameshift (c) Silent (d) Missense (e) Duplication

d

Which enzyme proofreads during replication?

(a) Ligase (b) Telomerase (c) DNA polymerase (d) RNase H (e) Helicase

c

Which chromosomal event produces balanced gametes?

(a) Nondisjunction (b) Segregation (c) Unequal crossing over (d) Inversion (e) Translocation

b

Which process creates recombinant chromosomes?

(a) Translation (b) Independent assortment (c) Crossing over (d) RNA editing (e) DNA methylation

c

Meiosis II separates:

(a) Homologues (b) Sister chromatids (c) Tetrads (d) Chromatin domains (e) Nucleoli

b

Which inheritance pattern skips generations often?

(a) Autosomal dominant (b) X-linked dominant (c) Autosomal recessive (d) Y-linked (e) Codominant

c

Which inheritance is exclusively maternal?

(a) X-linked (b) Autosomal dominant (c) Mitochondrial (d) Y-linked (e) Codominant

c

Which phenomenon causes variable phenotype in females?

(a) Inversion (b) Chromosome gain (c) X-inactivation mosaicism (d) Mitochondrial dilution (e) Translocation

c

Recombination frequency of 50% indicates:

(a) Complete linkage (b) Same gene (c) Separate chromosomes (d) Mitochondrial inheritance (e) Structural variation

c

Which histone modification typically increases transcription?

(a) Methylation (b) Deamination (c) Acetylation (d) Hydroxylation (e) Glycosylation

c

Which region of a gene binds transcription factors?

(a) Coding region (b) Terminator (c) Promoter (d) Poly-A site (e) UTR

c

Which RNA splicing modification joins exons?

(a) Helicase unwinding (b) Deamination (c) Ligation by spliceosome (d) Methylation (e) Telomerase activity

c

Which enzyme joins fragments of lagging strand?

(a) Ligase (b) Helicase (c) Primase (d) Telomerase (e) RNase H

a

Which direction does DNA polymerase read the template?

(a) 5’→3’ (b) 3’→5’ (c) Both ways (d) Randomly (e) Only in S phase

b

What forms after homologous chromosome pairing?

(a) Barr body (b) Tetrad (c) Chromatid loop (d) Operator (e) Enhancer

b

Which stage of meiosis does crossing over occur?

(a) Metaphase II (b) Prophase I (c) Anaphase I (d) Telophase II (e) Metaphase I

b

Which disease is X-linked recessive?

(a) Huntington disease (b) Cystic fibrosis (c) Hemophilia A (d) Achondroplasia (e) Trisomy 21

c

Which disorder is autosomal dominant?

(a) Sickle cell (b) Hemophilia B (c) Achondroplasia (d) Albinism (e) Tay-Sachs

c

Which disorder is autosomal recessive?

(a) Achondroplasia (b) Hemophilia (c) Cystic fibrosis (d) Huntington disease (e) Marfan syndrome

c

Which gene mutation causes retinitis pigmentosa (dominant form)?

(a) CFTR (b) FGFR3 (c) Rhodopsin (d) BRCA1 (e) HEXA

c

Which concept explains one gene influencing many traits?

(a) Epistasis (b) Pleiotropy (c) Penetrance (d) Dominance (e) Recombination

b

Which phenomenon occurs when two genes affect one trait?

(a) Penetrance (b) Polygenic inheritance (c) Nondisjunction (d) Mutation (e) Codominance

b

Heritability close to 1 indicates:

(a) Mostly environmental effects (b) Mostly genetic effects (c) No variation (d) Only epigenetic control (e) Mutation only

b

What is the helical repeat of DNA?

(a) 34 Å per 10 bp (b) 10 Å per 2 bp (c) 100 Å per 12 bp (d) 25 Å per 20 bp (e) 5 Å per base

a

Which bond holds the two DNA strands together?

(a) Phosphodiester bonds (b) Covalent bonds (c) Hydrogen bonds (d) Peptide bonds (e) Sulfhydryl bonds

c

Which protein forms the mitotic spindle?

(a) Actin (b) Tubulin (c) Myosin (d) Kinase (e) Dynein

b