6 from chromosomes to genomes

Question 1

structure of deoxyribonucleic acid (DNA)

Answer 1

double helix: two polynucleotide chains that coil around each other
- DNA codes genetic instructions for the development, function, growth and reproduction of organisms

Question 2

Define and know a nucleotide

Answer 2

a sub-unit of DNA consisting of a phosphate group,
a nitrogenous base and a sugar

phosphate group - circle
pentose sugar - pentagon
nitrogenous base - rectangle

Question 3

Complementary base pairs of nitrogenous bases

Answer 3

Adenine - Thymine
Guanine - Cytosine

Question 4

Define and describe the function of a gene

Answer 4

a section of a chromosome that codes for a protein through the order of the nucleotide base sequence

Question 5

explain alleles - hetero and homo

Answer 5

alleles: the different forms of a gene
heterozygous: two different alleles of a gene
homozygous: two identical alleles of a gene

Question 6

Differentiate genes and alleles

Answer 6

alleles are forms of genes whereas a gene is a section of a chromosome that codes for a protein

Question 7

define genome

Answer 7

the sum total of an organism’s DNA

Question 8

explain the nature of homologous choromosomes with reference to gene loci

Answer 8

homologous: matching pairs of chromosomes that have the same genes at the same positions (loci)

Question 9

define autosome

Answer 9

any pair of homologous chromosomes that are identical in appearance in both males and females

Question 10

define and know the diff sex chromosomes

Answer 10

a pair of chromosomes that differ in males and females of a species; allosomes
XX - female
XY - male

Question 11

Define haploid and diploid

Answer 11

diploid (2n): two copies of each chromosome in each set
- only somatic cells (46)

haploid (n): one copy of each chromosome in each set
- only gametes (23)

Question 12

Describe the purpose of a karyotype

Answer 12

karyotype: an image of chromosomes from a cell arranged in an organised manner
- a visual representation that can be used to identify chromosome abnormalities

Question 13

explain how karyotype is produced

Answer 13

• cytogeneticists capture an image of chromosome sets from a camera attached to a microscope
• image transfers to computer software that analyses and generates a karyotype

Question 14

know what characteristics used to create karyotype

Answer 14

• size
• position of the centromere
• banding patterns

Question 15

Detect chromosomal abnormalities on karyotype

Answer 15

aneuploidy: the presence of an abnormal number of chromosomes

Question 16

Outline how chromosomal abnormalities may occur

Answer 16

• changes in the total no. of chromosomes
• changes involving part one of chromosome
• changed arrangements of chromosomes

Question 17

Define and know the difference bw monosomy and trisomy

Answer 17

trisomy: a cell has three copies of a particular chromosome that is normally present as a homologous pair

monosomy: a cell has only one copy of a particular chromosome that is normally present as a homologous pair

Question 18

define sexual reproduction

Question 19

define/ know the difference between haploid and diploid

Question 20

define homologous chromosomes & identify chromosome, chromatid, centromere, sister chromatids

Question 21

define gametes of males and females, somatic cells

Question 22

Phases of meiosis and events occurring in each phase, and order events occur.

Question 23

End result (outcomes) of meiosis/why this is necessary.

Question 24

Cause of variability – crossing over and independent assortment (define, recognize)

Question 25

What happens when meiosis goes wrong? Ie. Non-disjunction

Question 26

what is the waist of a chromosome called

Answer 26

centromere: the position where the chromatids are held together in a chromosome

Question 27

Draw and name the 4 shapes of chromosome

Answer 27

MSAT

metacentric: centromere in the middle
- p and q arms are equal in length
submetacentric: centromere towards one end
- q arms approx. twice the length of p arms
acrocentric: centromere is very close to one end
- p arms are very short
telocentric: centromere is at the tip
- no p arms

Question 28

relo bw complexity of an organism and no. of genes and chromosomes it has