8.2 DNA and chromosomes

Question 1

give four ways prokaryotic DNA differs from Eukaryotic DNA?

Answer 1

shorter
not associated with proteins
circular
cells do not have chromosomes

Question 2

what proteins are DNA molecules in eukaryotes associated with?

Answer 2

histone proteins

Question 3

Name the 2 organelles of eukaryotes which contain DNA?

Answer 3

mitochondria

chloroplasts

Question 4

name the term for the position on a chromosome that a specific gene occupies

Answer 4

locus

Question 5

what is meant by the term homologous chromosome

Answer 5

the gene location is the same on both chromosomes but the allele that codes for the specific gene differs

Question 6

how many chromosomes do humans have?

Answer 6

diploid number is 46

therefore humans have 46 chromosomes

Question 7

how many pairs of chromosomes do humans have?

Answer 7

23 pairs

Question 8

describe the structure of dna in prokaryotic cells

Answer 8

dna molecules are shorter
dna molecules for a circle
dna molecules are not associated with protein molecules
cells do not have chromosomes

Question 9

describe the structure of dna in eukaryotic cells

Answer 9

dna molecules are longer
dna molecules form a line (are linear) and occur in association with proteins called histones, this forms chromosomes
the mitochondria and chloroplasts of eukaryotic cells also contain dna, dna is similar to that of prokaryotic cells

Question 10

describe the structure of a chromosome

Answer 10

a thread-like structure made of protein and DNA and DNA by which hereditary information is physically passed from one generation to another

Question 11

define chromatid

Answer 11

one of the two strands of a chromosome that are joined together by a single centromere prior to division

Question 12

define chromatin

Answer 12

the material that makes up chromosomes.

it consists of DNA and the protein histone

Question 13

define homologous chromosomes

Answer 13

a pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features.
they are not necessarily identical, however as individual alleles of the same gene may vary, e.g. one chromosome may carry the allele for blue eyes, the other the allele for brown eyes.
homologous chromosomes are capable of pairing meiosis

Question 14

define allele, give an example

Answer 14

one of a number of alternative forms of a gene.

for example, the gene for the shape of pea seeds has two alleles: one for ‘round’ and one for ‘wrinkled’