Genetics Practice Exam

Question 1

Short wings in fruit flys is
a) Genotype
b) Phenotype
c) Affected by its environment
d) Determined by the genotype
e) All except A

Answer 1

e) All except A (Phenotype, affected by its environment and determined by the genotype)

Question 2

In nucleosome what is DNA wrapped around?

Answer 2

Histones

Question 3

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

Answer 3

b) the 30nm chromatin fibre is thicker than nucleosome

Question 4

During mitosis, metaphase has _______ amount of genetic material than at G1.

Answer 4

Double the

Question 5

Sister chromatids begin to move apart in animal cells during ______

Answer 5

anaphase

Question 6

An allele is ____________

Answer 6

A variant of a gene

Question 7

Mendel law of hereditary states that

Answer 7

Independent assortment of genes and segregation of alleles

Question 8

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?

Answer 8

YY

Question 9

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?

Answer 9

TT

Question 10

A 9:3:31 phenotypic ratio is a characteristic of the ___________. (Hint : Generation & hybrid)

Answer 10

F2 generation of a monohybrid cross

Question 11

How many alleles does the blood human typing gene have?

Answer 11

three (IA, IB, and i)

Question 12

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

Answer 12

e) all except d

Question 13

According to Chargaffs rules for DNA base composition, if DNA sample contained 10% guanine, the sample should have how much thymine?

Answer 13

40%

Question 14

Using this strand answer following:
3’ TACCGGACGTTTGCGATT 5’

1. What kind of mutation results if the second G changes to an A?
2. What kind of mutation results if the third G changes to a T?
3. What kind of mutation results if the second A changes to a C?

ANS is one of following mutations:
Missense
Nonsense
Frameshift
Silent

Answer 14

1. Silent
2. Nonsense
3. Missense

Question 15

When tryptophan is present in E.coli, what happens to the repressor protein for the trp orperon?

Answer 15

Changes shape and binds to repressor

Question 16

What happens when lactose is present in E.coli?

Answer 16

The repressor protein changes shape and doesn’t bind to the operator of the lac operon, allowing transcription of structural genes.

Question 17

_________ cut at specific sites in the double stranded DNA molecule

Answer 17

Restriction enzymes

Question 18

Remember:
Independent orientation of chromosomes in meiosis…

Answer 18

..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

Question 19

Remember:
Crossing over of chromosomes in meiosis…

Answer 19

…involves two chromatids, one from each chromosome in a homologous pair

… shuffles the alleles of genes on the same chromosome

Question 20

According to Meselson Stahl Experiment, DNA replication is..

Answer 20

Semi-conservative

Question 21

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

Answer 21

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)

Question 22

T/F on topic of central dogma, the amino acid sequence is formed from the mRNA code during translation.

Answer 22

True

Question 23

Which RNA (tRNA, mRNA or rRNA has a section of its nucleotide sequence called anticodon?

Answer 23

tRNA

Question 24

T/F does a repressor consist of a sequence of nucleotide bases?

Answer 24

False it does not

Question 25

T/F in repressible operons, the end- product of the metabolic pathway is the co-repressor.

Answer 25

True

Question 26

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

Answer 26

D) A and C made of phosphate!!

Question 27

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

Answer 27

c) uracil is one of its nitrogenous bases

Question 28

T/F In the Hershey Chase Experiment Radioactive phosphate from the bacteriophage was found in the centrifuged pellet, where the bacteria was.

Answer 28

True

Question 29

What’s DNA molecule made up of?

Answer 29

Sugar phosphate backbone, nitrogenous bases, double helix, one less oxygen, nucleotides joined by phosphodiester bonds

Question 30

What’s an allele?

Answer 30

Alter. version of a gene

Question 31

What’s a locus?

Answer 31

Gene location of chromosome

Question 32

What is mitosis?

Answer 32

Produces an exact copy of cells DNA

Question 33

Why does meiosis happen?

Answer 33

New alleles and combinations

Question 34

What is Meiosis I? Meiosis 2?

Answer 34

1. Divide # of chromosomes in half, but still want a copy of all the genes of each chromosome. 2. 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.

Question 35

Deviations from Mendels laws

Answer 35

traits on same chromosome, traits on sex chromosome, incomplete dominance, multiple alleles, codominance, lethal alleles

Question 36

Segregation of alleles

Answer 36

2 alleles for a character segregate during gamete formation and end up in different gametes

Question 37

Independent assortment of genes

Answer 37

during gamete formation, pair of alleles for one gene will segregate independently of a pair of alleles for another gene

Question 38

Chromosome genetic disorders

Answer 38

Error in cell division causing cells with too many or too little copies of chromosome

Question 39

Monosomy vs Trisomy

Answer 39

Lack of single chromosome vs carry additional copy ~ chromosome genetic disorder

Question 40

What’s nondisjuction during meiosis

Answer 40

Fail to separate both sister chromatids/homologous chromosomes stay together rather than being pulled apart

Question 41

Single gene genetic disorder

Answer 41

Caused by mutant gene, may be present on only one chromosome (dom) or both (recess) to exhibit genes

Question 42

Purines and Pyradmidines

Answer 42

Purines & Guanine Cyto, thymine and uracil

Question 43

Melson & Stahl - semi conservative DNA replication

Answer 43

each strand serves as a template for synthesis of new complementary strand

Question 44

Helicase

Answer 44

Unwind DNA

Question 45

Primase

Answer 45

Synthesizes RNA primer at 5’ end of leading fragment and at each of end okazaki fragment of lagging strand

Question 46

Ligase

Answer 46

Joins fragments of lagging strand on leading strand, joins 3’ end of DNA that replaced primer to rest of leading strand DNA

Question 47

Central Dogma of biology (rough generalization)

Answer 47

Go from double stranded strand of DNA and the message is transcribed into messenger RNA and then it’s translated into polypeptide

Question 48

mRNA

Answer 48

Nucleotides can be converted by translation into peptide/protein

Question 49

tRNA

Answer 49

has anticodon, transports specific amino acids to ribosome

Question 50

Trypt. Operon

Answer 50

Repressor system, tryptophan is corepressor binding and preventing polymerase from turning operon on… decline in graph

Question 51

DNA Gel Electrophoresis

Answer 51

DNA negatively charged, moves towards positive end

Question 52

PCR

Answer 52

Denature, anneal, extension

Question 53

CRISPR

Answer 53

Clustered regularly interspaced small palindromic repeats