CYTOGENETICS - PRELIM

Question 1

In pea plants, the allele for tall stalks (T) is
dominant over the allele for short stalks (t).
Suppose a cross between a tall pea plant and
a short pea plant produces 43 tall offspring
and 47 short offspring. If one of the tall
offspring is crossed with one of the short
offspring, what ratio of genotypes would be
most likely in their offspring?

Answer 1

1Tt :1tt

Question 2

In forming a chromatin, the double-stranded
DNA must bind with proteins that are rich in

Answer 2

arginine

Question 2

How many different types of chromosomes
are found in human female lymphocyte?

Answer 2

23

Question 3

Which involves the removal of a wrong
nucleotide on an unmethylated DNA strand
and its replacement with the correct one?

Answer 3

mismatch repair

Question 4

In transcription, what is the role of the sigma
factor?

Answer 4

It recognizes the promoter locus, which is
required to identify the site to be transcribed.

Question 5

If in a diploid organism two different alleles
of a gene are both expressed in a heterozygous individual, the condition is
termed

Answer 5

codominant

Question 6

An actin-rich “purse string” that draws tight
to separate daughter cells to complete
cytokinesisin cell division is a

Answer 6

cleavage furrow

Question 7

X-inactivation occurs by addition of () in the
DNA.

Answer 7

methyl groups

Question 8

Which of the following is characteristic of
the first meiotic division but NOT mitotic
division?

Answer 8

Homologous chromosomes pair

Question 9

The PO4-end of the DNA is also known as

Answer 9

5’ end

Question 10

In guinea pigs, short hair is dominant over
long hair. If a short haired SS guinea pig is
crossed with a long haired ss guinea pig,
what is the percent chance that the offspring
is short-haired?

Answer 10

1

Question 11

Which guides the RNA polymerase as to
what appropriate nucleotide is added to a
growing RNA?

Answer 11

DNA template

Question 12

The X chromosome of a mother has a
mutated recessive gene for coagulation
factor VIII. This defective coagulation factor
is non-functional and, therefore, causes
hemophilia characterized by difficult-tocontrol bleeding. Which of the following is
INCORRECT regarding this?

Answer 12

A father with the recessive gene is likely to
transmit it to his son

Question 13

Which of the following best describes the
law of segregation?

Answer 13

During the formation of gametes, the paired
unit factors separate, or segregate, randomly
so that each sex cell receives one or the
other with equal likelihood.

Question 14

Which is INCORRECT regarding sex
chromosomes?

Answer 14

X-inactivation primarily occurs in the
maternal X chromosome

Question 15

Which of the following is a faithful copy of
the information encoded in a gene?

Answer 15

mRNA

Question 16

At what stage of the cell cycle do the
chromosomes become dyads?

Answer 16

interphase

Question 17

During DNA replication, the DNA
polymerase adds the new nucleotide at the

Answer 17

-OH end

Question 18

Which feature is the same in the translation
process of prokaryote and eukaryote?

Answer 18

peptide formation by peptidyl transferase

Question 19

Which is true about the telomere?

Answer 19

It consists of repeated sequence of
TTAGGG.

Question 20

A gene for corn has two alleles, one for
yellow kernels and one for white kernels.
Cross pollination of yellow corn and white
corn results in ears of corn that have an
approximately even mix of yellow and white
kernels. Which term best describes the
relationship between the two alleles?

Answer 20

Codominance

Question 21

Which of the following is NOT used to
identify a chromosome?

Answer 21

shape

Question 22

A recessive gene in female X chromosome
is expressed in the phenotype when the
alleles are

Answer 22

homozygous

Question 23

Which of the following best describes the
law of independent assortment?

Answer 23

During gamete formation, segregating pairs
of unit factors assort independently of each
other

Question 24

Meiosis in males starts

Answer 24

at adolescence

Question 25

The cycle control mechanisms check the following except

Answer 25

Whether cellular contents are received equally by each of the daughter cells

Question 26

Which of the following cells enters the G0 phase and remain there for the life of the individual?

Answer 26

myocytes

Question 27

If two genes undergo independent assortment, which assumption is most likely true?

Answer 27

The genes are located on different chromosomes or are far apart on the same chromosome

Question 28

These are nucleotide sequences that are transcribed but are excised from the mRNA before translation into protein.

Answer 28

introns

Question 29

If a cell has a diploid number of 36 (2n=36), how many chromosomes will be present in each daughter cell at the end of meiosis II?

Answer 29

18

Question 30

A cross between two pea plants with genotypes RrYy and RrYy results in an F1 generation that is 25% RRYY, 50% RrYy, and 25% rryy. Which reason most likely explains why other possible genotypes are not present?

Answer 30

The loci of the genes are on the same chromosome and in close proximity with each other

Question 31

Human sex cells have () autosomes.

Answer 31

22

Question 32

Which of the following is a correct pair?

Answer 32

Transcription: nucleus

Question 33

In a dihybrid cross, if two heterozygotes (for both genes) are crossed, what will be the expected phenotypic ratios? (In the following order: dominant for both traits; dominant for the first trait recessive for the second; recessive for the first trait and dominant for the second; recessive for both traits)

Answer 33

9:3:3:1

Question 34

Suppose a white-furred rabbit breeds with a black-furred rabbit and all of their offspring have a phenotype of gray fur. What does the gene for fur color in rabbits appear to be an example of?

Answer 34

Incomplete Dominance

Question 35

During meiosis, the X and Y chromosome pair at the metaphase plate

Answer 35

True

Question 36

Chromosome Y has similar size and morphology as chromosome

Answer 36

22

Question 37

Which characteristic of the genetic code indicates that an amino acid may be coded by more than one codon?

Answer 37

degenerate

Question 38

How many different types of chromosomes are found in a human male lymphocyte?

Answer 38

24

Question 39

During which stage of mitosis do chromosomes divide at the centromeres?

Answer 39

anaphase

Question 40

This structure is responsible for the accurate segregation of the replicated chromosome during mitosis and meiosis.

Answer 40

centromere

Question 41

A cell with 20 chromosomes undergoes mitosis. How many daughter cells are created? () and each daughter cell has () chromosomes.

Answer 41

2, 20

Question 42

Phenotype refers to the () of an individual

Answer 42

actual physical appearance

Question 43

The Broad Thumb-Hallux syndrome is due to deletion 16p13.3. This indicates that the deletion is located at

Answer 43

sub-band 3

Question 44

Crossing-over may occur between X and Y chromosomes

Answer 44

True

Question 45

Which is INCORRECT regarding oogenesis in human?

Answer 45

It stops at metaphase I.

Question 46

Which of the following enzymes acts before the others in DNA replication?

Answer 46

primase

Question 47

Which is true about G2/M checkpoint?

Answer 47

It ensures that the cell has an adequate size

Question 48

How many chromatids are there in 2 (two) bivalents?

Answer 48

8

Question 49

Obesity is an example of genotype and environment interacting in order to produce

Answer 49

phenotype

Question 50

Who shows hemizygous traits?

Answer 50

brother

Question 51

Which characterizes a chromatid?

Answer 51

It is one of the two identical copies of DNA making up a duplicated chromosome

Question 52

Which triplet will be most vulnerable to UVL?

Answer 52

TTA