DNA chapter 7

Question 1

How are 2 strands of DNA linked ?

Answer 1

1) Nitrogenous bases

2) They are linked by means of H bonds.

Question 2

Purines

Answer 2

A and G are double ringed

Question 3

Pyrimidines

Answer 3

C and T are single ringed

Question 4

Explain DNA packaging

Answer 4

1) DNA molecules of eukaryotes linked with histone protein
2) Packaging is essential because Nucleus is microscopic and DNA can be extremity long.
3) Nucleosomes are formed: DNA wraps twice around 8 histone proteins, 2 of each type.
3) between the nucleosomes there is a linker DNA
4) 5th type of histone attached to the linking string near each nucleosome

Question 5

Why DNA is attracted to Histones ?

Answer 5

DNA is - cahrged and Histones are + cahrged

Question 6

What function does DNA packaging serves

Answer 6

1) Wrapping allows certain areas of DNA to be available for protein synthesis
2) Regulation of transcription process
3) helps to super coil chromosomes

Question 7

Whats Genome ?

Answer 7

complete sequence of DNA

Question 8

What is DNA profiling ?

Answer 8

Obtaining a specific DNA pattern from an organism determining an individuals DNA characteristics.

Question 9

What is satellite DNA ?

Answer 9

Highly repetitive DNA clustered in discrete areas \

1) These sequences can jump from one location to another on the chromosome.

Question 10

What is structural DNA ?

Answer 10

1) Highly coiled DNA that does not have a coding function
2) Occurs around centro-mere
3) Near the ends of chromosomes

Question 11

Polymorphism

Answer 11

Most of our DNA is similar to the DNA of other people

1) However specific regions that show significant variation are called Polymorphism

Question 12

What are short tandem repeats

Answer 12

STRs are short sequences of DNA, normally of length 2-5 base pairs, that are repeated numerous times in a head-tail manner, i.e. the 16 bp sequence of “gatagatagatagata” would represent 4 head-tail copies of the tetramer “gata”.

Question 13

only 1 point of origin in bacterial dna

Answer 13

Because DNA is much smaller

no histones

Question 14

Where does the energy for DNA replication is derived from ?

Answer 14

Deoxynucleoside triphosphate molecule
contains 3 phosphate groups
2 phosphates are lost
provides energy for the nucleotides

Question 15

What isi Central Dogma ?

Answer 15

Info passes from genes on DNA to RNA copy and the RNA copy then directs the production of proteins at the ribosomes by controlling the sequence of amino acids.

Question 16

What re punctuation codons ?

Answer 16

Start and stop codons are called punctuation codons

Question 17

Methylated DNA

Answer 17

Inactive DNA is highly methylated
For instance, In females, X chromosomes are highly methylated.
Methylated genes are not transcribed or expressed.

Question 18

What are repressor proteins ?

Answer 18

Binds to the segment of DNA called silencers.Prevents transcription of the segment of that particular region.

Question 19

What are transcription factors ?

Answer 19

Transcription factors are proteins that help turn specific genes “on” or “off” by binding to nearby DNA.

A typical transcription factor binds to DNA at a certain target sequence. Once it’s bound, the transcription factor makes it either harder or easier for RNA polymerase to bind to the promoter of the gene.

1) Activators
2) Repressor :his repression can work in a variety of ways. As one example, a repressor may get in the way of the basal transcription factors or RNA polymerase, making it so they can’t bind to the promoter or begin transcription.

Question 20

Structure of Ribosomes

Answer 20

Ribosomal RNA+ Protein
Large subunit+ small subunit
Built in nucleolus of eukaryotic cells
Prokaryotic ribosomes are smaller thaneukaryotic ribosomes .
Between small and large sub unit, there is a binding site for mRNA.

Question 21

Where does the amino acid attaches on the tRNA?

Answer 21

3 prime end of the tRNA

Question 22

What is translocation

Answer 22

Movement of tRNA’s from one site to others.

Question 23

What is the cause of sickle cell disease ?

Answer 23

Only one amino acid changes in the sequence of hemoglobin–Hemoglobin

Question 24

how are the H bonds formed in secondary structure ?

Answer 24

Between Oxygen from the carboxyl group of one amino acid and the Hydrogen from amino group of the other.
1) it doesn’t involve the interaction of side chains.

Question 25

What are conjugated proteins ?

Answer 25

Proteins containing non-polypeptide groups like hemoglobin.

Question 26

What kind of interactions cause Tertiary structure of proteins.

Answer 26

1) Hydrogen bonds – between polar side chains.
2) Di sulfide bridges –covalent bonds between Sulfur atoms
3) Ionic bonds – between + and - charged side chains.
4) Hydrophobic interactions— Van der Waals between hydrophobic side chains.

Question 27

Examples of globular proteins

Answer 27

1) Insulin

2) Haemoglobin

Question 28

Splicing mRNA increases the no of diff proteins in an organisms

Answer 28

Exons may rearrange themselves after the removal of introns– resulting in diff possible proteins