3.2 Chromosomes

Question 1

chromosomes of prokaryotic cells

Answer 1

• singular chromosome = only one copy of each gene
• coiled up in nucleoid region
• genes are needed for basic life processes
• chromosome is makes, no histones
• second copy is made before binary fission

Question 2

plasmids in prokaryote bacteria

Answer 2

small extra DNA molecules
- small, circular, naked
- few genes that are not essential for cell function but might be helpful (eg. antibiotic resistance)
- not replicated at the same time as chromosome (cell can have many copies)
- can be transferred between prokaryotic cells

Question 3

plasmids are also used…

Answer 3

by scientists to artificially transfer genes between species

Question 4

audioradiography

Answer 4

• grown with thymine nucleotides with radioactive hydrogen isotope
• e. coli cells placed on dialysis membrane and lysed with enzymes
• cell contents applied to photgraphic emulsion palced in dark
• radioactive isotopes reacted with emultion making dark areas
• dark areas= presence of DNA

Question 5

conclusion of cairn’s technique

Answer 5

• e.coli has single cirular chromosome
• provided evidence for semi conservative replication

Question 6

eukaryotic chromosomes

Answer 6

• linear strands of dna in helix
• nucleosomes formed by wrapping dna around histones
• coiled into chromatin during interphsse
• supercoiled to form characteristic chromosome shape in mitosis

Question 7

Eukaryotic cells possess…

Answer 7

multiple chromosomes with different genes

Question 8

each chromosome carries….

Answer 8

a different set of genes in a specific order

Question 9

chromosomes can vary by

Answer 9

• length (number of base pairs in dna molecule)
• position of the centromere

Question 10

all individuals of a species…

Answer 10

have same chromosomes with same gene/locus

Question 11

genome:

Answer 11

complete set of genetic info in organism

Question 12

genomic size:

Answer 12

vary among organisms

Question 13

proportion of DNA

Answer 13

that acts as functional genes is variable

Question 14

homologous chromosomes

Answer 14

• same size and structure, same sequence of genes, may have different alleles for genes
• to interbreed two organisms must have homologous chromosome sets
• each chromosome type comes from the egg and otehr comes from the sperm to make homogolous pairs
• unless motehr gives x and father gives y (not homogolous)

Question 15

diploids

Answer 15

• 2 homologous pairs
• 2 copies of each gene
• 46 chromosome in human
• somatic cell

Question 16

haploids

Answer 16

• 1 chromosome
• 1 copy of each gene
• 23 chromosome in human
• gamete/sex cell

Question 17

sexual reproduction

Answer 17

haploid sperm and egg cells fuse into fertilization to produce a diploid zygote, which divides in mitosis to form embryo

Question 18

chromosome number is…

Answer 18

fundemental characteristic that defines a species

Question 19

organisms with different numbers of chromosomes are…

Answer 19

unlikely to be able to interbreed successfully

Question 20

chromosome number does not equal

Answer 20

complexity

Question 21

number of chromosomes in a species is known as the

Answer 21

N number

Question 22

chromosome number tends to be…

Answer 22

conserved across millions of years of evolution

Question 23

in rare cases, chromosomes can…

Answer 23

fuse or split during evolution to change the chromosome number of species

Question 24

sex determination

Answer 24

XX - female
XY- male

Question 25

x chromosome

Answer 25

• large with centromeme in the center
• x carries many genes in non-homologous region that is not in Y chromosome

Question 26

y chromosome

Answer 26

small with a centromere near the top
- SRY gene on Y leads to male development

Question 27

eggs

Answer 27

produced by females and have XX chromosomes

Question 28

sperms

Answer 28

produced by males and have XY chromosomes

Question 29

karyogram

Answer 29

diagram or photgraph of the chromosomes present in a nucleus of eukaryote cell arranged in homologous pais of decreasing length

Question 30

karyotype

Answer 30

property of the cell described by number and tyoe of chromosomes in nucleus

Question 31

3 key features to identify chromosomes

Answer 31

• seen in metphase most clearly
• stains give chromosome distinctive banding pattrn
• micrograph arranges in size and bandin pattern

Question 32

trisomy

Answer 32

having a third (extra) copy of a chromosome

Question 33

monosomy

Answer 33

having only one (missing) copy of a chromosome