Mendelian Genetics

Question 1

what are alleles

Answer 1

• each variation of a gene, which encodes for a slightly different protein
• are in pairs and represented by 2 letters

Question 2

what is a phenotype

Answer 2

the physical appearance due to a specific gene

Question 3

what is a genotype

Answer 3

genes(alleles) possessed by indivudals

Question 4

what is homozygous

Answer 4

an individual who has 2 identical alleles of a gene

Question 5

what is heterozygous

Answer 5

an individual who has 2 different alleles of a gene

Question 6

what is a dominant allele

Answer 6

A ‘strong’ allele which dominates over the other, causing that phenotype to emerge

Question 7

what is a recessive allele

Answer 7

A ‘weak’ allele which is dominated by the dominant allele, thus its phenotype not being present

Question 8

what are co-dominant alleles

Answer 8

alleles which are equally strong, thus creating mixtures of the phenotype of each allele in an individual

Question 9

what is a locus

Answer 9

the physical position of a gene on a chromosome

Question 10

what is a carrier

Answer 10

an individual who has a recessive allele that does not affect their phenotype, yet still has that allele present

Question 11

what is a punnet grid +use

Answer 11

• it is a diagram that shows all the possible combinations of alleles for a particular trait
• used to predict the outcome of genetic crosses (inheritance)

Question 12

who was Mendel

Answer 12

• austrian priest who investigated inheritance
• used pea plants to experiment
• not first person to do this work, first person to count and quantify genetic crosses

Question 13

what are mono-hyrbrid crosses

Answer 13

crossing pure bred individuals with a different allele for a specific trait

Question 14

what is a di-hybrid cross

Answer 14

a cross between two individuals that differ with two traits

Question 15

What is Mendel’s third law (law of independent assortment)

Answer 15

• genes do not influence each other with regard to sorting alleles into gametes
• Genes which are located on different chromosomes segregate independently from one another during gamete formation

-ALLELES OF GENES ON NON-HOMOLOGOUS CHROMOSOMES ASSORT INDEPDENTLY DURING MEIOSIS

Question 16

what are linked genes

Answer 16

genes that are located very close to one another on the same chromosome

-don’t follow Mendel’s second law, crossing over less likely to occur

Question 17

what is Mendel’s first law (law of dominance)

Answer 17

In a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.

Question 18

what is Mendel’s second law (law of segregation)

Answer 18

During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then “recombined” at fertilization, producing the genotype for the traits of the offspring.

Question 19

what is an example of co-dominance + both multiple alleles

Answer 19

blood type

Question 20

what are autosomal sex chromosomes

Answer 20

22 pairs of autosomes, 1 pair of sex chromosomes
-sex chromosomes control male (XY) and female (XX)
-

Question 21

what determines the sex of the offspring, the genetic makeup of the sperm or the genetic makeup of the egg

Answer 21

the genetic makeup of the sperm (X or Y) determine the gender

Question 22

what is sex-linkage

Answer 22

• genes carried by sex chromosomes

- sex-linkage is the assosiation of a trait with gender (gene controls traits on a sex chromosome)

Question 23

where do males and females recieve x-linked genes from

Answer 23

• male from mom (1copy): one allele for a particular trait

- female from both parents (2 copies)

Question 24

what are the symbols for sex-linked genes

Answer 24

• XA=normal allele

- Xa= recessive allele

Question 25

what are heterozygous females with X-linked disorders called

Answer 25

carriers

Question 26

what are examples of sex-linkage disorders

Answer 26

• hemophilia

- color blindness

Question 27

what is hemophilia

Answer 27

• sex linked
• woman is carrier
• recessive
• 50% of sons inherit disease, 50% of daughters carriers
• daughters of sons will be carriers, sons unaffected (only girls receive X-chromosome)

Question 28

what is color blindness

Answer 28

-inability to see certain colors
-common: inability to see red and green
-x-linked disorder
-ressive
-males usually have it
-

Question 29

what are autosomal disorders

Answer 29

• disorders which affect males and females equally
• dominant and recessive types
• takes only 1 copy of gene to cause disorder
• if child inherits diesease, at least one parent has it

Question 30

example of autosomal disorder

Answer 30

-cystic fibrosis

Question 31

what is a pedigree

Answer 31

-a chart of genetic history of family over generations

Question 32

why is a pedigree chart used

Answer 32

• to deduce is trait is dominant or recessive, inherited, sexlinked or autosomal
• to deduce the genotype of indivudals
• to deduce the probability of a child having a condition

Question 33

tips to read a pedigree chart

Answer 33

• if most males have it, its X-linked
• if its a 50/50 ratio of male and women; autosomal
• if the disorder is autosomal dominant, one of the parents must have disorder
• if autosomal recessive, none of the parents has to have the disorder to be heterozygous