genetics

Question 1

what is genetics

Answer 1

Examines how DNA sequences in chromosomes (genes) result in different traits (phenotypes)
Studies how genes & traits are passed on from one generation to another
i.e. the study of heredity

Question 2

what did gregor mendel do?

Answer 2

performed genetic crosses in peas and observed they have specific traits in specific pattern (either or)
either purple or white
wrinkled or smooth

Question 3

what is a cross

Answer 3

it is mating, pairing specific parents with specific traits to produce off spring

Question 4

what is a pure breeding plant (pure strain)

Answer 4

plant wheree all their ancestors showed the same traits 100% of the time.

Question 5

define phenotype

Answer 5

observable characteristics based on genotype

Question 6

define genotypee

Answer 6

set of genes in a organism (responsible for its traits)

Question 7

what are true breeding parents called

Answer 7

the P generation

Question 8

what are the offspring of those parents called

Answer 8

f1 generation (filial or child)

Question 9

what are the offspring of f1 and f1 called?

Answer 9

F2 generation

Question 10

what is it called when you cross two different true breeding varieties

Answer 10

hybridization

Question 11

menders experiment purple vs white flowers:explain

Answer 11

mendel cross bred pure breeding purple and white flowers
used pollen from white to fertilize purple eggs
result : all f1 hybrids have purple flowers
same result when pollen from purple and eggs from white was used

Question 12

what is the result of menders experiment

Answer 12

all offspring f1 have purple flowers regardless of having one white and one purple parent

Question 13

what is the law of segregation

Answer 13

Each gamete only carries 1 copy (allele) of each gene (since only have 1 copy of each chromosome)
Lets call our flower colour gene ‘A’ for simplicity
Fuse 2 haploid gametes to form 1 diploid zygote
Each zygote (each F1 plant) will have 2 copies of each gene – 1 from each parent
Each F1 plant will have 1 purple allele & 1 white allele

Question 14

define allele

Answer 14

different versions of the same gene

Question 15

explain why all f1 offspring of purple and white flowers were purple

Answer 15

because purple (A) is dominant over white (a) 
therefore wherever purple shows up it will mask white
consequently white is recessive: will not show up alongside purple

Question 16

explain second part of mendels experiment

Answer 16

cross breeds f1xf1

offspring shows both purple and white in a 3;1 RATIO\

Question 17

what is the locus of an allele

Answer 17

the location of the gene

Question 18

what is homozygous

Answer 18

Both alleles at a locus are the same

e.g. AA or aa

Question 19

what is heterozygous

Answer 19

The 2 alleles at a locus are different

e.g. Aa

Question 20

what are menders 4 concepts

Answer 20

Different alleles account for variations in inherited characters

For each character an organism inherits 2 alleles; 1 from each parent

if the 2 alleles at a locus differ, the dominant allele determines the organism’s appearance
The recessive allele has no noticeable effect on the organism’s appearance

Law of segregation
2 alleles for a heritable character separate (segregate) during gamete formation & end up in different gametes

Question 21

what is you are testing more than one gene?

Answer 21

dihybrid crosses

Question 22

how do you do dihybrid?

Answer 22

FOIL TRAITS

Question 23

WHAT are the two assortment hypotheses

Answer 23

Independent assortment
Genes (& corresponding characteristics) associate separately
In a gamete, receiving a certain allele for a gene does not influence which allele is received for a different gene*

Dependent assortment
Genes (& corresponding characteristics) associate together

Question 24

what phenotypic ration does independent assortment result in

Answer 24

9:3:3:1

Question 25

multiplication rule?

Answer 25

Probability of 2 or more independent events occurring together is calculated by multiplying the probability of each event. Key word: “And”

Question 26

addition rule?

Answer 26

Probability of 2 or more mutually exclusive events is calculated by adding their probabilities. Key words: “Either” “Or”

Question 27

what are the 5 inheritance patterns

Answer 27

``` autosomal recessive autosomal dominant x linked recessive x linked dominant y linked ```

Question 28

explain autosomal recessive

Answer 28

equal freq in sexes, skips generations, affected offspring born to unaffected parents

Question 29

explain autosomal dominant

Answer 29

equal freq in sexes, both sexes transmit to offspring, does not skip gens, unaffected parents do not transmit

Question 30

x linked recessive

Answer 30

males>females affected affected sons born to unaffected mothers, never passes from father to son

Question 31

x linked dominant

Answer 31

females > malees | does not skip gens

Question 32

y linked

Answer 32

only males affected passed from father to son does not skip gens

Question 33

what gender are sex linked genes more phenotypically expressed?

Answer 33

males

Question 34

females and their x chromos

Answer 34

inherit two x chromosomes therefore would need two copies of the recessive allele to show recessive phenotype

Question 35

males and their xy chromos

Answer 35

nothing can mask the recessive x linked gene

Question 36

examples of sex linked x traits

Answer 36

eye colour colour blindness haemophilia

Question 37

what are the three types of dominance

Answer 37

complete dominance incomplete dominance co-dominance

Question 38

explain complete domincance

Answer 38

phenotypes of heterosexuals zygote and dominant homo are identical

Question 39

explain incomplete dominance

Answer 39

2 difference alleles for 1 gene are BOTH expressed (intermediate) not an exact blend something shows through for both

Question 40

explain co-dominance

Answer 40

2 different alleles for 1 gene are BOTH FULLY expressed

Question 41

define epistasis

Answer 41

A gene at one locus alters the phenotypic expression of a gene at a different locus

Question 42

define pleotropy

Answer 42

A single mutation that has multiple effects (produces multiple phenotypes)

Question 43

define neomorphy

Answer 43

A mutation causes altered function - either expression at a different place or time, or a novel (new) function\

Question 44

define multifactorial

Answer 44

a trait is influenced by multiple phenotypes and environmental factors

Question 45

define polygenic

Answer 45

a trait is influenced by multiple genes

Question 46

what is the epistatic gene

Answer 46

thee gene that is responsible for masking/supressing | THINK DOG EEXAMPLE THERE IS A PATHWAY HAS TO GO THROUGH EPISTATIC GENE FIRST

Question 47

explain pleiotropy

Answer 47

1 gene is associated with many traits because genes are often active in many plaecees eex: sickle cell anemia and albinism

Question 48

give an example of multifactorial traits

Answer 48

height and heart disease/cancer

Question 49

explain polygenic traits

Answer 49

you will see an additive affect off different alleles/genes | either you will have an additive or no

Question 50

penetrance and expressivity

Answer 50

Penetrance Proportion of individuals of a certain mutant genotype that exhibit the mutant phenotype Quantitative Depends on modifiers, epistasis, & environment Expressivity Severity of the mutant phenotype generated by a particular allele Qualitative Depends on genetic background & environment

Question 51

explain x inactivation

Answer 51

Females condense & (almost completely) de-activate 1 of their 2 X-chromosomes during early embryonic development Barr-body = condensed X chromosome Normal females will have 1 barr-body & 1 uncondensed X chromosome per cell Normal males will not have barr-bodies

Question 52

what is lyon hypothesis

Answer 52

Females are mosaics Which X chromosome becomes a barr-body is initially random Humans: occurs at about day 10 Daughter cells will inherit the same pattern of inactivation expressed by the original cell