Lab 1

Question 1

What is a chromosome?

Answer 1

Structures made of DNA and protein that contain numerous genes which encode the proteins in our bodies

Question 2

What is a karyotype & when is it done?

Answer 2

A karyotype is a photograph or diagram of all the
chromosomes in a cell arranged in a particular order.
Done at metaphase so the dyads are more condensed and easier to visualize.

Question 3

What does a somatic cell contain?

Answer 3

A somatic cell contains 44 autosomes (nonsex
chromosomes), or 22 homologous pairs of
autosomes, and 2 sex chromosomes.

Question 4

What is a homolog?

Answer 4

A single unduplicated chromosome. Each homolog is similar but not
identical to the other homolog in the pair

Question 5

Another name for tetrad?

Answer 5

Bivalent & duplicated homologous chromosome pair.

Question 6

Another name for dyad?

Answer 6

Duplicated chromosome

Question 7

What is a centromere?

Answer 7

A condensed region on the chromosome that provides the attachment site for the kinetochore

Question 8

What does colchicine do?

Answer 8

Inhibits microtubule formation required to form the spindle fibers so that mitosis does not proceed past metaphase.

Question 9

Turner syndrome

Answer 9

Only one X and no Y chromosome.

Question 10

How are chromosomes distinguished from one another?

Answer 10

Size, Location of centromere, and banding patterns.

Question 11

Location of centromere:

Answer 11

Metacentric – centromere is near the middle

Submetacentric – centromere is slightly off center

Acrocentric – centromere is significantly off center

Telocentric – centromere is at the end.

Question 12

What are primary constrictions?
What are secondary constrictions?

Answer 12

Centromere
They are usually the site of rRNA gene.

Question 13

How are chromosomes stained?

Answer 13

They are stained using a Giesma stain

Question 14

Chromosome abnormalities involving one chromosome?

Answer 14

Deletion: part of the chromosome is absent.
Duplication: section of chromosome is repeated
Inversion: section of chromosome is upside down.

Question 15

Chromosome abnormalities involving two chromosomes?

Answer 15

Simple Translocation: A piece of a chromosome is attached to another chromosome.
Reciprocal Translocation: Two different chromosomes exchange pieces.

Question 16

What is crossing over?

Answer 16

Genetic exchange that occurs during meiosis. It occurs between two chromosomes that are the same number.
Occurs between duplicated chromosomes in a tetrad.

Question 17

Familia type of Down syndrome

Answer 17

Not caused by nondisjunction.
Caused by Translocation.
Involves chromosomes 14 & 21.

Question 18

Hypotonic Solution

Answer 18

Low solute concentration, high water concentration.
In karyotyping, they make the cell swell, this separates the chromosome so that they are easier to count.

Question 19

What is Nondisjunction?

Answer 19

Failure of chromosomes to separate normally during cell division.

Question 20

Two Types of Chromosomal Inversion-

Answer 20

Pericentric Inversion- Includes the centromere.
Paracentric Inversion- Doesn’t include the centromere

Question 21

Position Effect

Answer 21

The expression of a gene can be altered, and the gene itself remains intact.
With a position effect, you are changing the physical
position of the gene on the chromosome, and that
change affects the expression of the gene.

Question 22

Silencer/Condensed region

Answer 22

Example of a position effect.
Condensed region: Genes in highly
condensed regions of the chromosome are not expressed well.
Silencer: Genes are not expressed when they should be.

Question 23

Enhancer

Answer 23

A sequence that increases transcription, so the gene would be overexpressed.

Question 24

What are telomeres?

Answer 24

Repeated sequences on the ends of chromosomes that prevents chromosomal ends from attaching to one another.

Question 25

Reactive end

Answer 25

When the telomere breaks, a reactive end is formed. The reactive ends can be joined by DNA repair enzymes to create translocation between two nonhomologous chromosomes.

Question 26

Why might down syndrome occur? (Trisomy 21)

Answer 26

It might occur when crossing over does not take place between homologous chromosomes during meiosis during prophase 1.

Question 27

What is Robertsonian Translocation?

Answer 27

Translocation that can occur between any acrocentric chromosomes that are numbered. This can lead to down syndrome. Fertilization with gamete 1: Monosomy 21 develops Fertilization with gamete 2: Familial down syndrome.

Question 28

A type of Hemophilia occurs _____

Answer 28

On genes that encode blood clotting factors. The gene is located on the X chromosome. It involves an Inversion.

Question 29

The first step of gene expression:

Answer 29

Transcription.

Question 30

When a chromosome that is not a sex chromosome is lost, it is always lethal. (True/False)

Answer 30

True

Question 31

What is nondisjunction? what can it result to?

Answer 31

An event in which the chromosomes do not segregate properly. This can result in a change in chromosome number.

Question 32

What is an alloploid organism?

Answer 32

An organism that contains sets of chromosomes from two or more species.

Question 33

Types of nondisjunction?

Answer 33

Meiotic non-disjunction: Occurs during meiosis. Mitotic non-disjunction: Occurs during mitosis.

Question 34

Ways in which chromosome numbers can vary?

Answer 34

Mitotic non-disjunction Meiotic non-disjunction Alloploid.

Question 35

Complete nondisjunction:

Answer 35

All chromosomes undergo nondisjunction and migrate to one of the daughter cells.

Question 36

When do abnormalities in chromosomes normally occur?

Answer 36

After fertilization takes place.

Question 37

What is mosaicism?

Answer 37

When an organism contains a subset of cells that are genetically different from those of the rest of the organism. This depends on the timing and location of the original abnormal event.

Question 38

What is autopolyploid?

Answer 38

An increase in the number of chromosomes set within a single species.

Question 39

what is a Metacentric chromosome?

Answer 39

A chromosome that has equally centered centromere with arms with equal lengths.

Question 40

what is a sub-metacentric chromosome?

Answer 40

A chromosome that has arms a bit off-centred, with arms that are distinctly unequal in length.

Question 41

what is an acrocentric chromosome?

Answer 41

Centromeres are located nearer to one end than to the other. The arms are unequal in length.

Question 42

What is used to show karyotype bands?

Answer 42

Giemsa Bloodstain. G-Q-R bands.

Question 43

Each homolog is ________ but not _________to the other homolog in the pair

Answer 43

Similar; Identical

Question 44

What is a centromere

Answer 44

A condensed region on the chromosome that provides the attachment site for the kinetochore.

Question 45

Kinetochore:

Answer 45

Group of proteins that attach to the centromere. They pull the sister chromatids apart during cell division.

Question 46

How to distinguish chromosomes from one another:

Answer 46

Size, banding pattern & Location of centromere.

Question 47

Karyogram

Answer 47

The display of the karyotype

Question 48

What causes cru Du Chat?

Answer 48

Chromosomal deletion of chromosome 5. Region on p arm is deleted.