BSI Lecture 4 DNA Structure

Question 1

Chromosomes

Answer 1

contain long strands of DNA and associated proteins

Question 2

How many chromosomes do humans have?

Answer 2

46

Question 3

How many pairs of autosomes (non-sex chromosomes) do humans have?

Answer 3

22

Question 4

What are the types of sex chromosomes?

Answer 4

X and Y

Question 5

What is a Karyotype?

Answer 5

It is the display of all chromosomes in a cell

Question 6

What is an allele?

Answer 6

One of two or more alternative forms of a gene that arise by a mutation and are found in the same place on a chromosome

Question 7

What constitutes a normal Karyotype?

Answer 7

Humans have 46 chromosomes total. 22 pairs of autosomes (non-sex chromosomes) and a pair of XX or X and Y sex chromosome

Question 8

When does the chromosomes have to be packaged very tightly in an organized manner?

Answer 8

During mitosis

Question 9

When preparing for division, DNA is packed into the _________ chromosomes.

Answer 9

Mitotic

Question 10

How many levels of packaging are there?

Answer 10

4

Question 11

What level of packaging is it when threadlike mass of genetic material (DNA and histone proteins) form “beads on a string” (11nm structure)?

Answer 11

Level 1

Question 12

What is a nucleosome?

Answer 12

Basic structural unit of a chromosome. Histones, DNA, Linker Region

Question 13

How many turns of DNA helix are wound around the octomeric core of histones?

Answer 13

2

Question 14

What is the role of histones in DNA packaging?

Answer 14

Acts as spools for DNA helix to wrap around its octomeric core.

Question 15

What is a linker region?

Answer 15

A linker region is the DNA you see between the two histones or “beads”

Question 16

Octomeric core consists of two copies of each of the 4 core histone protein ____, ____, ____, and ____

Answer 16

H2A, H2B, H3, H4

Question 17

Histones are contained in the _______ ________

Answer 17

octomeric core

Question 18

Level 2 packaging, what is the chromatin fiber width?

Answer 18

30nm

Question 19

What is the purpose of DNA packaging?

Answer 19

Organize and fit all of the DNA into the nucleus.

Question 20

What is the difference between mitotic chromosome and an interphase chromosome?

Answer 20

Mitotic chromosomes are ready for replication and interphase chromosomes are not.

Question 21

Can the same gene produce mRNA and tRNA?

Answer 21

No

Question 22

Do genes encode lipids and carbohydrates?

Answer 22

No, only proteins are encoded. Lipids and carbohydrates are synthesized.

Question 23

Loops are condensed into chromosomes (700nm). At what level does this occur?

Answer 23

Level 4

Question 24

What are telomeres?

Answer 24

DNA sequence at the ends of the chromosomes

Question 25

Telomeres are repeated DNA sequences which allow the ends of chromosomes to be replicated and also to protect the ends from being mistaken by the cell as broken DNA

Answer 25

True

Question 26

What is a chromatid?

Answer 26

One of the paired and parallel strands of a duplicated chromosome joined by a single centromere.

Question 27

What is a sister chromatid?

Answer 27

A duplicate copy of a chromatid joined by the centromere.

Question 28

What is a centromere?

Answer 28

Specialized DNA sequence that allows duplicated chromosomes to be separated during mitosis.

Question 29

Where do the mitotic spindle binds?

Answer 29

Centromere

Question 30

________ is the part of the cell cycle when the cell is not dividing.

Answer 30

Interphase

Question 31

Packaging of interphase: What percent of the chromosome are highly condensed?

Answer 31

10%

Question 32

What are heterochromatin?

Answer 32

Highly condensed chromosome

Question 33

Genes that are considered "off" are located in areas of ______________

Answer 33

heterochromatin

Question 34

Most regions of the interphase chromosome are less condensed, these area is called ____________

Answer 34

Euchromatin

Question 35

What level of mitotic chromosome does euchromatin resemble?

Answer 35

Level 2

Question 36

Each strand of DNA is made up of ________

Answer 36

Nucleotides (deoxyribose, phosphate, and base)

Question 37

DNA strands run in _________ direction.

Answer 37

Opposite

Question 38

DNA strands are held together by hydrogen bonds between ________

Answer 38

Bases

Question 39

The backbone of the DNA strand is called the _________

Answer 39

Sugar-phosphate backbone

Question 40

The two strands of nucleotides forms a ________

Answer 40

Double helix

Question 41

The basic building blocks of a nucleotide are

Answer 41

Ribose (sugar), phosphate, and a base

Question 42

Nucleoside consists of

Answer 42

ribose and base (no phosphate)

Question 43

What are the 2 Purines and are they single or doubled ringed?

Answer 43

Adenine and Guanine, they are double ringed

Question 44

What are the 3 Pyrimidines and are they single or doubled ringed?

Answer 44

Cytosine, Thymine, and Uracil, they are single ringed.

Question 45

How are nucleotides linked?

Answer 45

Via phosphodiester bonds to form a strand of DNA

Question 46

What bond forms between 3'-OH group of one sugar and 5'-phosphate group of another?

Answer 46

Phosphodiester bonds

Question 47

Define: Gene

Answer 47

A gene is usually defined as a segment of DNA that contains the instructions for making a particular protein (or RNA, if that is the final product).

Question 48

What type of RNA is the only one translated into protein?

Answer 48

mRNA

Question 49

What are the "other" types of RNA?

Answer 49

snRNA, miRNA

Question 50

RNA are single or double stranded molecules?

Answer 50

single

Question 51

RNA is composed of ______________ acids

Answer 51

ribonucleic

Question 52

RNA has an OH group at the _____' position of sugar.

Answer 52

2'

Question 53

Besides complementary pairing, what are the other functions of Purines and Pyrimidine?

Answer 53

Energy, metabolism, protein synthesis, regulation of enzyme activity and signal transduction

Question 54

The difference between ribose and deoxyribose is that ribose has an "OH" and deoxyribose has a single "H" at which carbon?

Answer 54

2'