chapter 13 - DNA

Question 1

what is DNA

Answer 1

• deoxyribonucleic acid, found in the nucleus of each cell, contains genetic information that determines the structure of the cell and the way it functions
• structure: double helix (sugar phosphate backbone and nitrogen bases), made up of nucleotides (phosphate, deoxyribose sugar, base)

Question 2

what is a nitrogen base

Answer 2

• pyrimidines: cytosine and thymine
• purines: adenine and guanine
• pyrimidines always pair with purines (AT: 2 H bonds, CG: 3 H bonds)

Question 3

what is DNA replication

Answer 3

• formation of new DNA molecules that are identical to each other
• process: takes place during interphase of mitosis
  1. enzyme helicase unwinds the original DNA
  2. enzyme DNA polymerase brings the free complimentary nucleotides to the complimentary base
  3. new identical DNA strand is made (1 old and 1 new strand)
  4. DNA winds back up

Question 4

DNA vs RNA

Answer 4

• DNA: double stranded, contains ACGT, deoxyribose sugar

- RNA: single stranded, contains ACGU, ribose sugar

Question 5

what is the role of DNA

Answer 5

• protein synthesis (transcription and translation)
• lipid and carbohydrate synthesis
• inheritance of mitochondrial DNA (mtDNA)

Question 6

what is protein synthesis

Answer 6

• gene expression, copying DNA information into messenger RNA (mRNA) known as the process of transcription, and then translating the messages into a series of amino acids to form a protein

Question 7

what is transcription

Answer 7

1. enzyme helicase unwinds DNA strand
2. RNA polymerase binds to one strand of DNA
3. adds complimentary nucleotides to DNA strand
4. mRNA detaches from DNA
5. mRNA leaves nucleus via nuclear pores and attaches to ribosomal RNA (rRNA)
6. DNA double helix winds itself back up

Question 8

what is translation

Answer 8

1. mRNA attaches to ribosomal RNA (rRNA)
2. the correct tRNA brings the correct anticodon and amino acid to the mRNA
3. rRNA moves along mRNA to read the next triplet codon
4. next tRNA brings the correct anticodon and amino acid to triplet codon
5. peptide bonds form between the amino acids
6. tRNA detaches from mRNA to go and find another amino acid to attach too
7. repeat steps 2-6
8. new protein chain is produced from amino acids (peptide bonds)

Question 9

what are the different types of DNA

Answer 9

• DNA: very large molecule, two strands of nucleotides joined by bases and twisted into a double helix
• nuclear DNA (nDNA): DNA found in the nucleus
• mitochondrial DNA (mtDNA): DNA found in the mitochondria

Question 10

what are the different types of RNA

Answer 10

• RNA: large molecule composed of a single strand of nucleotides
• messenger RNA (mRNA): RNA molecule that carries the code for protein synthesis from the DNA in the nucleus to the ribosomes where the protein is made
• transfer RNA (tRNA): small RNA molecule that transfers the correct amino acid to the ribosome for inclusion in the protein molecule being made

Question 11

what is lipid and carbohydrate synthesis

Answer 11

• there are no genes that control lipid and carbohydrate synthesis
• this protein requires proteins and enzymes

Question 12

what is the inheritance of mitochondrial DNA

Answer 12

• structure: small circular molecules, 5-10 mtDNA in each mitochondrion
• function: 37 genes (24 code for making tRNA, 13 make enzymes involved in cell respiration)
• inheritance: from mother only (mtDNA from sperm is destroyed upon fertilisation), can trace ancestors through mtDNA