Macromolecules: DNA

Question 1

DNA

Answer 1

deoxyribonucleic acid
chemical unit of information in most organisms
located in nuclei of cells
stores & transmits information
composed of repeating nucleotides (Adenine, Thymine, Guanine, Cytosine)
Structure: 2 complementary strands, double helix, bases joined by weak H-bonds
backbone = phosphate & deoxyribose

Question 2

Chromosomes

Answer 2

= condensed form of chromatin (DNA + protein, no discernible shape)
appear only during cell division - short, thick, rod-like structures, composed of many genes

Question 3

Genes

Answer 3

segments of DNA, complete sequence of bases required to manufacture protein
100+ genes for simplest cell - proteins > enzymes > reactions
1 gene = 1 protein/ RNA molecule

Question 4

Karyotypes

Answer 4

picture/computer-generated photo, chromosomes arranged largest to smallest
sex chromosomes = XY, determines sex
autosomes = all other chromosomes
locus = specific location on chromosome

Question 5

DNA Replication

Answer 5

cell divison (mitosis, meiosis - growth, repair, perpetuation) requires copy of DNA to pass onto daughter cells

1. Unwind DNA molecule (enzymes unwind & split(
2. New DNA strands (DNA polymerase joins free nucleotides to their complementary base on template strand (complementary base pairing)
3. Rewind DNA strand (four new DNA strands re-twist, each containing one old & new strand > semi-conservative replication)

Question 6

RNA

Answer 6

ribonucleic acid
temporary store of genetic information, used to pass onto protein synthesis
single strand, Adenine, Uracil, Guanine, Cytosine

Question 7

mRNA

Answer 7

messenger RNA

used in transcription of DNA from nucleus to ribosomes in the cytoplasm (codons match tRNA anti-codons)

Question 8

tRNA

Answer 8

transfer RNA
used in translation to bring correct amino acid to ribosome to match mRNA codon - nucleotides folded into clover leaf shape, exposed three = anti-codon

Question 9

Protein Synthesis

Answer 9

Transcription (DNA > RNA)
1. segments of DNA strands partially unwind, separate
2. free mRNA nucleotides pair with exposed DNA bases by complementary base pairing
3. RNA polymerase links mRNA nucleotides to form mRNA strand
4. non-coding regions (introns) removed from mRNA strand leaving exons
5. “mature” mRNA strand moves to cytoplasm through nuclear pores & DNA strands rejoin & rewind
Translation (RNA > protein)
1. mRNA strand binds to ribosome in cytoplasm
2. “START” amino acid (methionine) brought into place by tRNA (tRNA anticodon must match complementary mRNA codon)
3. ribosome moves along mRNA strand, attaching appropriate tRNA anti-codons to mRNA codon.
4. enzymes bind each amino acid with peptide link, forming polypeptide chain. “unloaded” tRNA moleculles released and able to rebind with amino acids (in cytoplasm)
4. process continues until ribosome reaches “STOP” codon, mRNA detaches, protein breaks away, folds into tertiary shape, ready for use in the cell/exocytosis