Study Guide Exam 2

Question 1

Bacteria typically have a single chromosome- what shape is it?

Answer 1

Circular

Question 2

What is the name give to the complex of DNA and proteins that form a chromosome?

Answer 2

Chromatin

Question 3

Most cells contain 2 copies of each chromosome, one inherited from the mother and one from the father- what is the name given to the 2 copies of each chromosome?

Answer 3

Homologous Chromosomes

Question 4

Because the Y and X chromosome are different, as a pair, they are called…

Answer 4

Non-Homologous or Sex Chromosomes

Question 5

Define a Gene

Answer 5

Carrier of genetic information that codes for a protein of RNA molecule

Question 6

Is all DNA genes?

Answer 6

No, only about 2% of the human DNA codes for proteins AKA genes

Question 7

How many genes do humans have?

Answer 7

Around 20,000

Question 8

How many chromosomes do humans have?

Answer 8

46 Chromosomes or 23 Pairs

Question 9

What occurs during Interphase?

Answer 9

DNA replication occurs

Question 10

Where does DNA duplication begin?

Answer 10

It begins at an AT rich origin of replication sequence

Question 11

What are the ends of a chromosome called?

Answer 11

Telomeres

Question 12

What occurs during mitosis?

Answer 12

The nucleus and the 23 pairs of replicated chromosomes are divided into daughter cells

Question 13

When are chromosomes most easily visible?

Answer 13

During the mitotic phase

Question 14

What specialized DNA sequence allows one copy of each chromosome to be placed into each daughter cell?

Answer 14

Centromere

Question 15

What are the two classes of proteins that bind to DNA to form chromosomes?

Answer 15

Histones and Non-histone proteins

Question 16

What is a nucleosome?

Answer 16

DNA wrapped around histone proteins

Question 17

What can you say about the genes contained on the regions of interphase chromosomes that are more extended than other regions?

Answer 17

Euchromatin is less condensed and contains more transcribed genes that heterochromatin

Question 18

What happens to one of the two X chromosomes in females?

Answer 18

It becomes inactivated and forms a Barr Body

Question 19

As a DNA double helix replicates to form two new double helices, each new double helix contains one parental strand and one new strand of DNA. DNA replication is therefore known to be _____ ______

Answer 19

Semi Conservative

Question 20

Origins of replication are rich in what two bases?

Answer 20

A and T

Question 21

What is the name of the enzyme that separates the two strands of DNA in the double helix?

Answer 21

DNA Helicase

Question 22

What do single strand binding proteins do?

Answer 22

Bind to the opened replication fork strands and prevent it from closing

Question 23

At origins of replication, two replication forks are formed; DNA replication is thus known to be _______

Answer 23

Bidirectional

Question 24

What is the name of the small molecule that complementarily binds to the DNA to be replicated?

What enzyme synthesizes this molecule?

Answer 24

RNA Primer

RNA Primase

Question 25

Why does DNA polymerase need this small RNA primer molecule before it can start synthesizing DNA?

Answer 25

DNA polymerase needs to start from a double strand. It needs the 3' carbon to form the next phosphodiester bond

Question 26

The leading strand is synthesized _______

Answer 26

Continuously

Question 27

The lagging strand is synthesized _________

Answer 27

Discontinuously

Question 28

What are the name of the fragments of DNA that make up the new strand complementary to the lagging strand?

Answer 28

Okazaki Fragments

Question 29

Name 3 differences between DNA and RNA

Answer 29

DNA uses deoxyribose, RNA uses ribose, DNA is a double helix, RNA is a single strand, DNA uses thymine, RNA uses Uracil

Question 30

Is all DNA genes?

Answer 30

No, only 2% of human DNA is genes

Question 31

If we want to make a single strand of mRNA from DNA where would we start? How do we know where to start transcription?

Answer 31

The promoter sequence aids in the finding of the AUG start site

Question 32

In DNA replication, the double helix was unwound by helicase. What does this job in RNA synthesis?

Answer 32

RNA polymerase opens the transcription bubble

Question 33

How do we know where transcription should stop?

Answer 33

A termination sequence will denote where it should stop

Question 34

What three things occur during mRNA processing

Answer 34

1- Splicing of Introns 2- 5' Methylated guanine cap is added 3- Polyadenylation tail is added

Question 35

The following is a sequence of DNA. Transcribe this into RNA and then translate it into protein 5' CCT CTT ACA CGC CGG GCA TTA 3'

Answer 35

RNA- GGA GAA UGU GCG GCC CGU AAU Protein- GLY GLU CYS ALA ALA ARG AS

Question 36

What is a codon and where do you find it?

Answer 36

3 nucleotides- in mRNA from a gene coding sequence

Question 37

What is an anticodon and where do you find it?

Answer 37

The 3 nucleotide sequence complimentary to the codon found on the anticodon loop of tRNA

Question 38

If the codon Is GGC, what is the anticodon?

Answer 38

CCG

Question 39

Describe control of gene expression at each step below DNA -> pre mRNA -> mRNA in nucleus -> mRNA in cytoplasm -> protein -> active protein

Answer 39

1) Controlling when and how often a gene is transcribed 2) Controlling how the transcript is spliced 3) Controlling if the mRNA leaves the nucleus and goes into the cytoplasm or not 4) Controlling which mRNAs are translated 5) Activating or inhibiting the protein function

Question 40

Is the Lac operon found in prokaryotes or eukaryotes?

Answer 40

Prokaryotes

Question 41

Gene Lac 1 codes for what protein?

Answer 41

Repressor Protein

Question 42

Is the repressor protein always present?

Answer 42

Yes

Question 43

What does the repressor protein do in the absence of lactose?

Answer 43

Binds to the operator sequence and block RNA polymerase access to the promoter

Question 44

What does the repressor protein do in the presence of lactose?

Answer 44

Lactose is converted to allolactose and binds to the repressor protein