Genetics Practice Exam Flashcards
Short wings in fruit flys is
a) Genotype
b) Phenotype
c) Affected by its environment
d) Determined by the genotype
e) All except A
e) All except A (Phenotype, affected by its environment and determined by the genotype)
In nucleosome what is DNA wrapped around?
Histones
Which statement is true about hierarchical arrangement of DNA?
a) chromatin loops smaller than 30nm chromatin fibre
b) the 30nm chromatin fibre is thicker than nucleosome
c) nucleosomes are smaller than DNA molecule
b) the 30nm chromatin fibre is thicker than nucleosome
During mitosis, metaphase has _______ amount of genetic material than at G1.
Double the
Sister chromatids begin to move apart in animal cells during ______
anaphase
An allele is ____________
A variant of a gene
Mendel law of hereditary states that
Independent assortment of genes and segregation of alleles
Testcross - Pods of pea plant, green trait (Y) is dominant over yellow (y). If 45 out of 92 F1 pods were yellow, what was the green parents genotype?
YY
Testcross - Trait for a flower position on top of plant (t) is recessive to axial flower position (T). If half of the F1 plants produced flowers at the top, what was the axial parents genotype?
TT
A 9:3:31 phenotypic ratio is a characteristic of the ___________. (Hint : Generation & hybrid)
F2 generation of a monohybrid cross
How many alleles does the blood human typing gene have?
three (IA, IB, and i)
What kind of meiotic non-disjunction can lead to an XXY son?
a) at meiosis I in formation of eggs
b) at meiosis I in formation of sperm
c) at meiosis II in formation of eggs
d) at meiosis II of the Y chromosome in formation of sperm
e) all except d
e) all except d
According to Chargaffs rules for DNA base composition, if DNA sample contained 10% guanine, the sample should have how much thymine?
40%
Using this strand answer following:
3’ TACCGGACGTTTGCGATT 5’
- What kind of mutation results if the second G changes to an A?
- What kind of mutation results if the third G changes to a T?
- What kind of mutation results if the second A changes to a C?
ANS is one of following mutations:
Missense
Nonsense
Frameshift
Silent
- Silent
- Nonsense
- Missense
When tryptophan is present in E.coli, what happens to the repressor protein for the trp orperon?
Changes shape and binds to repressor
What happens when lactose is present in E.coli?
The repressor protein changes shape and doesn’t bind to the operator of the lac operon, allowing transcription of structural genes.
_________ cut at specific sites in the double stranded DNA molecule
Restriction enzymes
Remember:
Independent orientation of chromosomes in meiosis…
..Means that each homologous paid sorts it’s maternal and paternal homologues into gametes independently of every other pair.
..shuffles the alleles of genes on different chromosomes
Remember:
Crossing over of chromosomes in meiosis…
…involves two chromatids, one from each chromosome in a homologous pair
… shuffles the alleles of genes on the same chromosome
According to Meselson Stahl Experiment, DNA replication is..
Semi-conservative
Which is true about DNA replication?
a) primase unwinds the double helix
b) DNA polymerase extends the DNA from an RNA primer strand
c) The Okazaki fragments are formed in 3’ to 5’ direction, using lagging strand as template.
d) B and C
d) B and C
(DNA polymerase extends the DNA from an RNA primer strand, The Okazaki fragments are formed in 3’ to 5’ direction, using lagging strand as template)
T/F on topic of central dogma, the amino acid sequence is formed from the mRNA code during translation.
True
Which RNA (tRNA, mRNA or rRNA has a section of its nucleotide sequence called anticodon?
tRNA
T/F does a repressor consist of a sequence of nucleotide bases?
False it does not
T/F in repressible operons, the end- product of the metabolic pathway is the co-repressor.
True
Nucleotides are:
a) made of ribose, phosphate and a base
b) made of a ribose, a sulfate and a base
c) the building blocks of DNA
d) A and C
e) B and C
D) A and C
made of phosphate!!
Which is true of RNA?
a) it’s double stranded
b) it has one less oxygen in its ribose
c) uracil is one of its nitrogenous bases
d) A and C
c) uracil is one of its nitrogenous bases
T/F In the Hershey Chase Experiment Radioactive phosphate from the bacteriophage was found in the centrifuged pellet, where the bacteria was.
True
What’s DNA molecule made up of?
Sugar phosphate backbone, nitrogenous bases, double helix, one less oxygen, nucleotides joined by phosphodiester bonds
What’s an allele?
Alter. version of a gene
What’s a locus?
Gene location of chromosome
What is mitosis?
Produces an exact copy of cells DNA
Why does meiosis happen?
New alleles and combinations
What is Meiosis I? Meiosis 2?
- Divide # of chromosomes in half, but still want a copy of all the genes of each chromosome.
- Variation allowing new allele gametes randomly receive one chromosome of each homologous pair…crossing over results in shuffle of genes within homologous chromosomes after fertilization.
Deviations from Mendels laws
traits on same chromosome, traits on sex chromosome, incomplete dominance, multiple alleles, codominance, lethal alleles
Segregation of alleles
2 alleles for a character segregate during gamete formation and end up in different gametes
Independent assortment of genes
during gamete formation, pair of alleles for one gene will segregate independently of a pair of alleles for another gene
Chromosome genetic disorders
Error in cell division causing cells with too many or too little copies of chromosome
Monosomy vs Trisomy
Lack of single chromosome vs carry additional copy ~ chromosome genetic disorder
What’s nondisjuction during meiosis
Fail to separate both sister chromatids/homologous chromosomes stay together rather than being pulled apart
Single gene genetic disorder
Caused by mutant gene, may be present on only one chromosome (dom) or both (recess) to exhibit genes
Purines and Pyradmidines
Purines & Guanine
Cyto, thymine and uracil
Melson & Stahl - semi conservative DNA replication
each strand serves as a template for synthesis of new complementary strand
Helicase
Unwind DNA
Primase
Synthesizes RNA primer at 5’ end of leading fragment and at each of end okazaki fragment of lagging strand
Ligase
Joins fragments of lagging strand on leading strand, joins 3’ end of DNA that replaced primer to rest of leading strand DNA
Central Dogma of biology (rough generalization)
Go from double stranded strand of DNA and the message is transcribed into messenger RNA and then it’s translated into polypeptide
mRNA
Nucleotides can be converted by translation into peptide/protein
tRNA
has anticodon, transports specific amino acids to ribosome
Trypt. Operon
Repressor system, tryptophan is corepressor binding and preventing polymerase from turning operon on… decline in graph
DNA Gel Electrophoresis
DNA negatively charged, moves towards positive end
PCR
Denature, anneal, extension
CRISPR
Clustered regularly interspaced small palindromic repeats
