Chapter 29 - DNA And Chromosomes

Question 1

Nucleic acid

Answer 1

• control the operation of cells
• found in the cytoplasm
• DNA and RNA are nucleic acids

Question 2

Deoxyribonucleic acid (DNA)

Answer 2

• contained in the chromosome
• each 4 cm long
• DNA is coiled around a protein called histone

Question 3

What are homologous chromosomes ?

Answer 3

• two chromosomes that form a pair
• in which genes are arranged along their length
• control identical characteristics like eye colour

Question 4

What are Genes ?

Answer 4

A length of DNA which carries genetic code for particular characteristic. It’s the genetic code for making a specific protein

Question 5

What are Allele ?

Answer 5

One of the alternative forms of the same gene. It carries different code for the same protein or characteristic

Question 6

Locus (no not the maths locus)

Answer 6

• the precise position of a gene in the chromosome

- alleles occupy the same loci

Question 7

Haploid n

Answer 7

• a cell that only has unpaired chromosomes
• it’s half of a diploid
• gametes are haploid

Question 8

Diploid 2n

Answer 8

• a cell which has homologous pairs
• somatic cells are diploid
• is double the haploid

Question 9

State what is DNA

Answer 9

• material of inheritance

- found in chromosomes

Question 10

Structure of a gene

Answer 10

• a chromosome is made of many genes
• a gene is the length of DNA
• each gene control one characteristic

Question 11

Structure of DNA

Answer 11

• a long molecule which forms a double helix
• made up of subunits called nucleotides
• each nucleotide is made up of 3 chemical groups
• the first group is sugar called deoxyribose sugar
• the second is nitrogenous base
• four nitrogenous bases are : adenine, thymine, guanine and cytosine
• group three is the phosphate part
• between bonds are weak hydrogen bonds ( two bonds between A and T and three bonds between G and C )

Question 12

Replication of DNA

Answer 12

• when cell divides by mitosis to form identical daughter cells
• new chromosomes must be formed before division
• DNA molecule makes copies of itself it’s called replication

Question 13

The semi- conservative replication of DNA

Answer 13

• DNA molecule unwinds
• it then unzips
• enzyme DNA polymerase is used to unzip
• allows complimentary strand to separate
• exposed base acts as template
• free nucleotides are are activated by extra phosphate
• complimentary pairing occurs
• backbone is formed by sugar-phosphate

Question 14

Importance of DNA replication

Answer 14

• provides identical copies of all genetic instructions
• minimize mistakes
• mistakes can lead to mutation
• mutation can lead to cancer
• mutation can contribute to evolution

Question 15

Transcription

Answer 15

• DNA in nucleus partly unwinds
• forms template for syntheses of mRNA
• called transcription
• base is transcribed to complementary base sequence of mRNA
• mRNA passes out the nucleus through the nuclear pores and goes to ribosomes

Question 16

Translation

Answer 16

• in ribosomes translation occurs
• amino acids are assembled onto the codons of the mRNA
• tRNA brings amino acids to the anticodon on it to the mRNA
• this forms polypeptide with peptide bonds

Question 17

Remember

Answer 17

• RNA have urasil (U) instead of thymine
• if anticodon on tRNA is UAC the codon on mRNA is AUG
• for every amino acid there is one or more codons but no codon codes for more than one amino acid
• this means the amino acids will fit into the correct order in the protein

Question 18

What is a chromosome

Answer 18

A long thread like structure in nucleus which carry genetic info and is composed of strands of DNA