3. Karyograms Flashcards Preview

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Flashcards in 3. Karyograms Deck (14):
1

How many chromosomes do prokaryotes have? How many do eukaryotes have? What do they do?

- pro: 1
- eu: different chromosomes that carry genes

2

How many chromosomes in humans? What do they do?

23 different chromosome types each of which carries a different group of genes

3

Define 'homologous' in terms of chromosomes.

chromosomes of one particular type - same genes in same sequence, but different alleles of those genes

4

Define 'alleles'

different forms of a gene

5

The number of chromosomes is a.....species

- characteristic feature of members of a species

6

When quoting numbers of chromosomes a species has, what number is usually quoted?

the diploid number - how many chromosomes are present in normal body cells

7

Give 5 examples and diploid chromosome number.

Homo sapiens (humans) - 46
Pan troglodytes (chimpanzee) - 48
Canis familiaris (dog) - 78
Oryza sativa (rice) - 24
Parascaris equorum (horse threadworm) - 4

8

What sort of nucleus do most plant and animal cells have? What do some cells have?

- diploid nucleus - nucleus contains pairs of homologous chromosomes
- haploid nucleus - only has one chromosome of each type

9

Name two cells that have haploid nucleus'?

gametes such as sperm and egg cells of humans

10

How is a diploid nucleus cell formed by two gametes?

gametes such as sperm and egg cells fuse together during fertilisation and produce one diploid cell - a zygote

11

Which pair of chromosomes determines your sex in humans? How?

the 23rd pair:
- two types of sex chromosome: X and Y
- XX: female
- XY: male

12

Define 'karyotype'.

the number and type of chromosomes present in a cell or organism

13

What is a karyogram?

- a photograph or diagram in which the chromosomes of an organism are shown in homologous pairs of decreasing length

14

Why are karyograms useful (general)? Give two examples of when a karyogram might be prepared.

so the chromosomes of an individual can be studied:
a) deducing the sex of an individual
b) diagnosing conditions due to chromosome abnormalities
- normal karyotypes: pair of each chromosome type including a pair of sex cells
- more or less than 2 of each pair = chromosome abnormality
- Down Syndrome: three of chromosome 21
- (males only) Klinefelter Syndrome: XXY (extra X)

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