SB3

Question 1

Describe the Structure if DNA

Answer 1

Chromosomes are located at the nucleus of the cell it consists of long molecules of DNA tightly packed by the protein Histone

Genes are very small sections of a chromosome

Double Helix refers to the spiral shape of the DNa

Bases are the part of the DNA containing genetic information

DNA backbone supports the base pairs but do not have genetic information

Question 2

What is a nucleotide?

Answer 2

Are nitrogen containing organic substances that form the basis of the nucleic acids DNA and RNA

Made of Phosphate,
Pentose sugar “Deoxyribose” in DNA or Ribose in RNA
Nitrogen containing base

Question 3

Sescribe the bases in DNA

Answer 3

Four types of bases
Adenine
Thymine
Cytosine
Guamine

Adenine base pairs with Thymine base with 2 hydrogen bonds
Cytosine base pairs with Guamine base with 3 hydrogen bonds

Question 4

Describe the different types of RNA

Answer 4

mRNA (Messenger RNA)
rRNa (Ribosomal RNA)
tRNA ( transfer RNA)

1. mRNA
   copies DNA code and carries the genetic information to the ribosome
   contains many sequences of 3 bases called codons
2. rRNA
   a single strand 100 to 300 nucleotides long,
   alongside proteins makes up the ribosome
   the site of protein synthesis
3. tRNA
   clover leaf shape, transfers amino acids to the ribosomes where proteins are synthesized
   bases in tRNA are called anticodons

Question 5

what are the stop codon combinations for mRNA

Answer 5

UAA UAG UGA

Question 6

Sescribe in short the stages of Protein Synthesis

Answer 6

1. Transcription of the genes in the nucleus to form a mRNA strand
2. Processing of the mRNA
3. Translation of the mRNA in a ribosome, a polypeptide chain is formed
4. modification of the protein

Question 7

Describe Transcription in Protein Synthesis in detail

Answer 7

1. the enzyme helicase breaks the hydrogen bonds between the bases in a specific region of a double stranded DNA in the nucleus
   this causes the two strands to separate
2. RNA polymerase binds to the base sequence called the promoter region.
   this determines which qay the RNA polymerase faces and which region is used as the template
3. RNA polymerase moves along the 5’ to 3’ direction in the DNA strand. as it passes over the DNA it begins to form a complementaru mRNA strand from free RNA nucleuotides in the nucleus
4. as the mRNA strand is producdd, the two strands of DNA begin to recoil behind it
5. when a terminator region is reached the DNA is no longer copied
   mRNA is now readu for the next stage of protein synthesis, translation

Question 8

Describe translation in detail

Answer 8

STAGE 1
the mRNA strand formed in the nucleus attaches to a ribosome out in the cytoplasm
the mRNA is attached at the start codon AUG at the 3’ end of the strand

2. transfer RNA molecules contain a sequence of three bases called anticodon, the tRNA molecule will bond with a complementary codon on the mRNA strand
3. as the ribosome moves along the mRNA another tRNA moves in the corresponding amino acid. the two acids are then join together with a peptide bond by an enzyme
4. another tRNA moves into the ribosome, adding another amino acid to the chin the first tRNA molecule is released and is free to collect another amino acid from the cytoplasm

5 This process continues until a stop codon is reached on the mRNA strand. aa there is not a corresponding tRNA for this sequence, the polypeptide chain is released

The polypeptide chain Wilson undergo post translational modifications for this able to function