Medelian Genetics

Question 1

Blending theory of inheritance (before Mendel)

Answer 1

Traits blend evenly in offspring through mixing of parents blood
Explains intermediate traits

Question 2

Mendel garden pea

Answer 2

• removed stamens from purple flower and transferred pollen to white flower
• control self fertilization and cross fertil.
• P was homozygous
• F1 was all purple, not pure breed. Heterozygous
• F2 both purple and white

Question 3

Law of segregation

Answer 3

• inheritance of single character
• genes exist in alternative versions called alleles
• for each characteristic, organism inherits 2 alleles one from each parent
• alleles differ, dominant determines organisms appearance
• allele pairs separate during gamete production

Question 4

Recessive alleles for albino coloration in animals

Answer 4

• expressed when both are recessive homozygous

- Aa brown mice can pass a allele so they carriers

Question 5

Testcross

Answer 5

To determine unknown genotypes

• mating between individual of unknown genotype and homozygous recessive Individual
• will show whether unknown genotype includes recessive allele
• identify dominat phenotype genotype

Question 6

Independent assortment (2 principle of Mendel)

Answer 6

Alleles at different loci (on different chromosomes) are inherited independently
-experiment with 2 or more different traits

Question 7

Chi-square

Answer 7

-if calculated value is smaller than tabulated value at the .5 probability than independent assortment is supported

Question 8

Polygenic inheritance (exception to Mendel one gene codes for one trait)

Answer 8

Single character many genes

Question 9

Incomplete dominance (exception to Mendel 1 gene codes for 1 trait)

Answer 9

Allele is not completely dominant, the other allele will have effect
Ex: snapdragons: pink F1 generation, heterozygote phenotype is different from either parent
-1 allele produces functioning protein. Other non-functional

Question 10

Co-dominance (exception to Mendel 1 gene codes 1 trait)

Answer 10

Both alleles produce protein that creates trait

Question 11

Pleiotropy (exception to Mendel 1 gene codes 1 trait)

Answer 11

Ex:sickle cell
-affects type of hemoglobin produced and shape RB
-causes anemia and organ damage
Single gene many phenotypes!!!
-Marfans syndrome: dominant allele ( responsible for tall. Curved spine. Elongated fingers)

Question 12

Epistasis (exception to Mendel 1 gene codes 1 trait)

Answer 12

• gene at one locus alters expression of a gene at another
• regulatory genes may give rise to epigenetics: turning on and off genes
• mice, black is B dominant. b is brown recessive.
• presence of second allele C determines pigment is expressed
• C is color expression. c is color inhibition. CC and Cc have black or brown. cc are white.

Question 13

Autosomal recessive disorder

Answer 13

• sickle cell. Cystic fibrosis. Albinism. Methemoglobinemia
• problem with recessive allele
• even though not expressed. Parents can be carriers.

Question 14

Autosomal dominant disorder

Answer 14

• one faulty dominant allele causes disorder
• Huntingtons, polydactyl, brittle bone
• person with disorder can be homo or hetero

Question 15

X-linked disorder

Answer 15

Faulty allele on X chromosome

• faulty recessive allele
• mother to son and daughter
• father to daughter
• color blind, hemophilia, duchenne
• male with faulty allele x have no other allele on Y to mask effect

Question 16

Faulty chromosome number

Answer 16

Chromosome pair fail to separate during meiosis.
-monosomy: chromosome with no pair
-trisomy: 3 copies of chromosome
Non disjunction: in meiosis 1 100% abnormal. Meiosis 2 50%

Question 17

Aneuploidy

Answer 17

Gametes with too many or too few chromosomes

Question 18

Monosomy

Answer 18

Turners syndrome

• non disjunction in 23 pair
• only X chromosome present
• 95% die

Question 19

Trisomy

Answer 19

Down syndrome 
-impotency in male
-21 non disjunction 
XXX super female 
XYY super male 
-delayed walking emotional difficulties 
XXY: Klinefelter syndrome

Question 20

Linkage

Answer 20

• result of two loci being located close together on same chromosome. Causes departure from independent assortment
• causes certain combo of genes to be over represented in indivdiaul gametes
• F1 wild type,
• no linkage expected 25%

Question 21

Linkage mapping

Answer 21

• tell how far apart loci are by proportion of F2 from a test cross that are recominants
• take number of recombinants and divide by total
• recombinants are F2 that do not resemble grandparents
• from r get distance between loci by multiplying r by 100 in map units
• farther away, higher r, more recominants