gene structure and chromosomal abnormalities

Question 1

what makes up the human genome?

Answer 1

Genes - exons and introns
intergenic regions
small DNA molecule in mitochondria

Question 2

how many bases in whole human genome?

Answer 2

3.2billion

Question 3

what is a gene

Answer 3

the basic physical and functional unit of heredity

Question 4

how many genes in human genome

Answer 4

20,000-23,000

makes up 2% of genome

Question 5

introns

Answer 5

AKA intragenic regions

non-coding regions found within genes

Question 6

intergenic regions

Answer 6

do not contain protein-coding sequences - between the genes

contain regulatory elements involved in switching genes on and off

Question 7

mitochondrial DNA

Answer 7

circular double-stranded DNA molecule
codes for 37 genes
inherited exclusively from oocyte - maternal pattern of inheritance

Question 8

what makes up chromatin?

Answer 8

DNA
RNA
protein

Question 9

what is the main protein in chromatin?

Answer 9

histones

Question 10

formation of chromatin

Answer 10

DNA wound around histones to form nucleosomes which are organised into solenoids.
Solenoids loop up into structure of chromatin

Question 11

types of chromatin?

Answer 11

euchromatin

heterochromatin

Question 12

euchromatin

Answer 12

open chromatin and prevalent in parts of genome being regularly used - where genes are switched on

Question 13

heterochromatin

Answer 13

condensed for of chromatin made up of tight loops - most abundant in parts of the genome where genes are switched off

Question 14

what do the light and dark stained parts represent on chromosomes?

Answer 14

light = open chromosome structure, euchromatin
dark = condensed chromosome, heterochromatin

Question 15

what is the p arm?

Answer 15

short arm structure of chromosome

Question 16

what is the q arm?

Answer 16

long arm of chromosome

Question 17

where is centromere located?

Answer 17

constricted point of chromosome, closer to top of chromosome

Question 18

how many DNA molecules are there in a chromosome?

Answer 18

1

Question 19

what introduces variation during meiosis?

Answer 19

crossing over
independent assortment
errors/ mutations in replication

Question 20

DNA damage in germline cells

Answer 20

changes cause heritable defects

Question 21

DNA damage in somatic cells

Answer 21

changes cause non-heritable local changes

Question 22

when does crossing over occur?

Answer 22

1st meiotic division

Question 23

mutations

Answer 23

drive evolution but can be pathogenic, causing disease

Question 24

when does crossing over occur?

Answer 24

1st meiotic division - prophase 1

Question 25

when does independent assortment occur?

Answer 25

before crossing over in first meiotic division

Question 26

what happens in crossing over

Answer 26

homologous chromosomes exchange genetic material at chiasma | introduces genetic variation

Question 27

which enzyme corrects mistakes by RNA polymerase?

Answer 27

MMR excision

Question 28

what is MMR excision

Answer 28

goes along newly made strand and looks for mistakes in base pairing by RNA polymerase - wrong bases and corrects them mismatch repair

Question 29

what happens independent assortment?

Answer 29

during anaphase 1 centromeres do not duplicate and divide so only one member of each pair of chromosomes migrate to each daughter cell - either maternal or paternal mix of chromosomes is different from cell to cell

Question 30

what is loss or gain of a chromosome called?

Answer 30

aneuploidy

Question 31

what is loss of a single chromosome

Answer 31

monosomy

Question 32

gain of one homologous chromosome

Answer 32

trisomy

Question 33

gain of 2 homologous chromosomes

Answer 33

tetrasomy

Question 34

what is addition of one or more complete haploid components

Answer 34

polyploidy

Question 35

turner syndrome

Answer 35

monosomy X

Question 36

nullisomic gametes

Answer 36

missing chromosomes | result in monosomic zygote

Question 37

disomic gametes

Answer 37

double no. chromosomes | results in trisomic zygote

Question 38

banding

Answer 38

looking at band pattern of homologous chromosomes to see if they are the same

Question 39

what is the most common trisomy?

Answer 39

16

Question 40

symptoms of downs syndrome

Answer 40

learning disorder issues with social skills shorter heart defects