human genome and chromosomes

Question 1

what phase does DNA replication occur in?

Answer 1

S phase

Question 2

what is a karyotype?

Answer 2

complete set of chromosomes in a species

Question 3

what is a kayogram?

Answer 3

an actual photograph of chromosomes arranged in homologous pairs

Question 4

what phase are karyograms usually taken in?

Answer 4

metaphase - chromosomes condense

Question 5

what is the short arm of the chromosome called?

Answer 5

the p arm

Question 6

what is the long arm of the chromosome called?

Answer 6

the q arm

Question 7

what are telomeres?

Answer 7

protective DNA and protein cap with repeating DNA which caps the end of the chromosome

Question 8

what happens to telomeres over time?

Answer 8

they shorten

Question 9

what does the centromere do?

Answer 9

keeps sister chromatids together
attaches to microtubules
repetitive DNA

Question 10

what is the G light band

Answer 10

light band of the DNA
gene rich
GC rich
early replication

Question 11

what is the G dark band?

Answer 11

gene poor
AT rich
late replicating

Question 12

what are the autosomes

Answer 12

chromosomes 1-22

Question 13

what are the sex chromosomes

Answer 13

chromosomes 23

Question 14

what is the haploid chromosome number?

Answer 14

23

Question 15

what is the diploid chormosome number?

Answer 15

46

Question 16

define aneuploidy

Answer 16

an abnormal number of chromosomes

Question 17

define pseduogene

Answer 17

non-functional copy of a gene

genes get duplicated and mutated

Question 18

what is disomy?

Answer 18

two copies of a chromosome

Question 19

what is polyploidy

Answer 19

gain one or more haploid sets of chromosomes

Question 20

what is translocation?

Answer 20

when one part of a chromosome breaks off and joins onto another chromosome

Question 21

what is a Robertsonian translocation?

Answer 21

two chromosomes joining at their centromere

Question 22

what causes down’s syndrome?

Answer 22

trisomy 21
robertsonian translocation (extra chromosome 21)
mosaicism

Question 23

give some features of downs syndrome

Answer 23

distinct facial expression
muscle hypotonia
congenital heart malformations
lower IQ - learning difficulties
distinct facial feature
may have single palm crease

Question 24

what causes Edwards syndrome?

Answer 24

trisomy 18

Question 25

what are some features of Edwards syndrome?

Answer 25

clenched hands with overlapping fingers | distinct feet and facial paterns

Question 26

what causes Patau syndrome?

Answer 26

trisomy 13

Question 27

what causes Klinefelter's syndrome?

Answer 27

extra X chromosome in males | XXY

Question 28

what are features of Klinefelter's?

Answer 28

infertility poorly developed secondary sexual characteristics tall

Question 29

what causes Turner's syndrome?

Answer 29

only 45 chromosomes | missing an X chromosome in females

Question 30

what are some features of Turner's syndrome?

Answer 30

``` dont have periods - primary amenorrhoea short poorly developed breasts low hairline congenital heart disease ```

Question 31

name some methods of prenatal diagnosis

Answer 31

amniocentesis chorionic villus sampling - testing placenta tissue non-invasive techniques e.g. ultrasound

Question 32

what is lyonisation?

Answer 32

X chromosome inactivation

Question 33

why is lyonisation needed?

Answer 33

so that female somatic cells only have one function X chromosome

Question 34

what are pseudoautosomal regions?

Answer 34

genes found on both X and Y regions

Question 35

what is the Barr body?

Answer 35

inactivated X chromosome

Question 36

what is the SRY?

Answer 36

sex determining region of the Y chromosome

Question 37

what is g banding?

Answer 37

A technique where you take a metaphase spread of chromosome on a glass slide, add trypsin and digest away some of the proteins so you’re left with some reproducible bands

Question 38

what are coding sequences?

Answer 38

encode proteins

Question 39

what are non-coding sequences?

Answer 39

intergenic regions and introns

Question 40

what are exons?

Answer 40

regions of genes that encode protein sequences

Question 41

what are introns?

Answer 41

non-coding regions between the exons in a gene

Question 42

what are control elements?

Answer 42

sequences like promoters and enhancers that regulate transcription.

Question 43

what is a pseudogene?

Answer 43

non-functional copy of a gene; arises from gene duplication followed by deleterious mutation in one copy.

Question 44

what is pre-mRNA?

Answer 44

first strand made after transcription

Question 45

what is splicing?

Answer 45

the process by which the introns are removed to give rise to the mRNA sequence which then codes for the protein

Question 46

what are features of Patau syndrome?

Answer 46

• Affects midline structures particularly: incomplete lobation of the brain, cleft lip, congenital heart disease

Question 47

how is down's syndrome tested for?

Answer 47

ultrasound imaging of nuchal translucency | 11-14 weeks