3.2 Chromosomes

Question 1

Chromosome

Answer 1

single double-stranded DNA molecule
- Chromosomes may contain thousands of unique genes on either stand
- Chromosomal structure differs between prokaryotic and eukaryotic organisms

Question 2

Prokaryotic Chromosomes

Answer 2

• do not possess a membrane-bound nucleus
• DNA is contained in a region called nucleoid
• only have a single chromosome (genophore)

Question 3

Eukaryotic Chromosomes:

Answer 3

• DNA is stored in a membrane-bound nucleus
• Nuclear pores allow transport of RNA to the cytosol
• Possess multiple linear chromosomes which carry many different genes

Question 4

Characteristic of DNA (Prokaryotic Chromosomes)

Answer 4

• DNA is circular and naked (not bond to proteins)
• Genome is more compact (usually no introns)
• Known as “naked DNA” because it is not organized around associated histone proteins

Question 5

Characteristic of DNA (Eukaryotic Chromosomes)

Answer 5

• DNA is bound to histone proteins to form chromatin
• The genome is less compact (has many introns)

Question 6

Plasmids

Answer 6

small circular DNA molecules that contain on a few genes an are capable of self -replication Additional circular DNA molecules that prokaryotic cells may possess

Question 7

Characteristic of Plasmids

Answer 7

• Can self-replicate and autonomously synthesize proteins (autonomous function)
• Prokaryotes can exchange plasmid by bacterial conjugation (through sex pili)

Question 8

Diploid

Answer 8

nuclei possessing pairs of homologous chromosomes
- Nuclei will posses a single gene copy (allele) for each trait
- All somatic (body) cell in the organism will be diploid, with new diploid cells created via mitosis
- Cells are present in most animals and many plants

Question 9

Haploid

Answer 9

nuclei possessing only one set of chromosomes
- These nuclei will possess a single gene copy (allele) for each trait
- All sex cells (gametes) in the organism will be haploid, and are derived from diploid cells via meiosis
- Haploid cells are also present in bacteria (asexual) and fungi (except when reproducing)

Question 10

Homologous chromosomes

Answer 10

chromosomes that carry the same sequence of genes but not necessarily the same alleles of those genes

Question 11

Homologous Chromosomes Characteristics

Answer 11

• Chromosomes share the same structural features (size, banding patterns, centromere position)
• Chromosomes share the same genes at the same loci positions
• Alleles may be different because bared chromosomes come from different origins (maternal vs paternal)

Question 12

Hererosomes

Answer 12

(sex chromosomes) - are what determine human sex

Question 13

Autosomes

Answer 13

are the remaining chromosomes in the organism (do not determine sex)

Question 14

Karyotypes

Answer 14

the number and types of chromosomes in a eukaryotic cell

Question 15

Karyogram

Answer 15

shows the chromosomes of an organism in homologous pairs of decreasing length
- Chromosomes of an organism are arranged into homologous pairs according to size

Question 16

Karyotyping

Answer 16

• Used to determine the gender of an unborn child (through the identification of the sex chromosomes)
• Used to test for chromosomal abnormalities

Question 17

Down Syndrome

Answer 17

a condition where an individual has three copies of chromosomes 21
- Caused by a non-disjunction event in one of the parental gametes
- The extra genetic material causes mental and physical delays in the way the child develops

Question 18

Autoradiography

Answer 18

a technique that uses X-ray film to visualize the two-dimensional distribution of a radioactively labeled substance.
- The image formed is called an autoradiograph

Question 19

Summary of Autoradiography Process

Answer 19

• Radioactive thymidine incorporated into DNA
• Chromosomes treated with silver bromide
• Radiation converts Ag+ ions to insoluable grains