T10- HOW ARE GENES ORGANISED IN CHROMOSOMES

Question 1

alleles

Answer 1

different versions of the same gene

Question 2

genotype

Answer 2

genetic constitution

Question 3

phenotype

Answer 3

the expression of the genetic constitution and interaction with the environment

Question 4

mendles concepts

Answer 4

• alternative versions of a gene account for variation in inherited characters
• for each character/trait an organism inherits 2 alleles, one from each parent
• if 2 alleles differ, the dominant allele determines phenotype, the recessive allele has no effect
• law of segregation - 2 alleles for a heritable trait are segregated during gamete formation-meiosis

Question 5

wild type gene

Answer 5

the dominant - predominant allele/variant

Question 6

mutant gene

Answer 6

the recessive - any other form of a gene distinct from the wild type

Question 7

P GEN

Answer 7

parental generation with true breeding organsism - homozygous AA aa

Question 8

homozygous

Answer 8

alleles both the same

Question 9

heterozygous

Answer 9

alleles different

Question 10

F1 GEN

Answer 10

Filial offspring, will all be heterozygous Aa because parents true breed

Question 11

F2 gen

Answer 11

crossing 2 F1 gen, this showed a random combo of 3:1 always

Question 12

thomas hunt morgan

Answer 12

used fruit fly model to look at genetics and interactions
- used a microscope to image chromosomes (karyotype) and saw structure of XX XY

Question 13

because of THM studies

Answer 13

he observed that mutant/recessive trait was more present in males suggesting that the gene/loci is on the X chromsomes

• as males only possess one X chromosome/allele, it is more likely for them to display the recessive trait and they only need one recessive allele unlike in females, who need 2 recessive alleles which is unlikely - displaying sex linked traits

Question 14

genetic linkage

Answer 14

if genes are close together on the same chromosome (loci are close)
- it is likely that they will be inherited together because less likely that they will be split apart during crossing over

Question 15

sex linkage

Answer 15

traits that are linked on the sex chromosomes

Question 16

autosomal linkage

Answer 16

linkage of traits seen on all other chromosomes other thansex

Question 17

recombination frequency

Answer 17

number of recombinant offspring / total offspring x 100

Question 18

using recombinant frequency

Answer 18

can create a genetic linkage map/ R.F used to calculate the linear order of genes on a chromosome - repeat with lots of different characteristics to find distances

Question 19

linkage explaining

Answer 19

if 2 genes are linked will see that obvious in the observed population of offspring - if crossing over has not happened then only 2 phenotypes seen
- if crossing over has occured, get 4 but in low frquency because it is very unlikely

Question 20

Aneuploidy

Answer 20

is the abnormal chromosome number
- monosomy - one chromo missing in zygote (2n-1) monosomic

• trisomy - one extra chromo in zygote (2n+1) trisomic
• polyploidy - extra full set of chromo (3n or 4n)

can lead to natural abortion or other diseases such as Down syndrome

Question 21

defective meiotic recombination leading to alternation of chromo structures

Answer 21

duplication - addition of a broken fragment resulting in a repetition of genetic information

deletion - of a chromo fragment

inversion - re addition of broken fragment in the wrong direction

translocation - movement of part of a chromosomes onto a different chromosome

resulting in disease

Question 22

non disjunctiion

Answer 22

this could occur in meiosis 1 or meiosis 2, which happens when incomplete separation of Homologous chromosomes

Question 23

what does recombiant frequency mean?

Answer 23

the greater the recombinant frequency, the further apart the loci for each gene
- because more recombinant offspring produced, so if loci are further apart, more likely to be separated during crossing over
- the closer the loci are the less recombinant offspring so the less R.F - this allows to produce a genetic map
anything less than 50% = on same chromosomes

Question 24

parental and recombinant phenotype

Answer 24

parental phenotype - the phenotype seen in parents
recombinant - new phenotype seen due to crossing over occuring