PRINCIPLES OF HEREDITY / MENDELIAN LAWS

Question 1

DEFINE GENE

Answer 1

unit of heredity

Question 2

DEFINE ALLELE

Answer 2

different forms of the same gene

Question 3

DEFINE GENOTYPE

Answer 3

all genes in an organism
-genetic constitution

Question 4

DEFINE PHENOTYPE

Answer 4

physical characteristics of genes
-influenced by environment
-result of genotype

Question 5

DEFINE HOMOZYGOTE

Answer 5

same alleles

Question 6

DEFINE HETEROZYGOTE

Answer 6

different alleles

Question 7

DEFINE AUTOSOMAL

Answer 7

non sex chromosomes

Question 8

DEFINE GONOSOMAL

Answer 8

sex chromosomes

Question 9

WHAT IS THE P GENERATION?

Answer 9

–parental
-dominant homozygote X recessive homozygote
-AA x bb

Question 10

WHAT IS THE F1 GENERATION?

Answer 10

– first filial generation, formed by the crossing of parental generation (AA x bb)
-descendent (children) are always heterozygotes (Ab)

Question 11

WHAT IS THE MONOHYBRID F2 GENERATION?

Answer 11

-second filial generation, crossing of F1
(Ab x Ab)
-descendants have different genotypes (AA, Ab,
Ab, bb)

GENOTYPE = 1:2:1
PHENOTYPE = 3:1

Question 12

WHAT IS A B1 BACKCROSS?

Answer 12

crossing parent with F1 (parent x F1) (AA x Aa)
-AA, AA, Aa, Aa → 1:1 (genotype) - same phenotype

Question 13

WHAT IS A TEST CROSS?

Answer 13

• crossing an unknown genotypic individual with a known homozygous recessive (PP or Pp x pp)
• can be used to determine the genotype of the unknown parent
  -Aa, Aa, aa, aa → 1:1 (genotype)

Question 14

DEFINE MONOHYBRID

Answer 14

observation of 1 allele

Question 15

DEFINE DIHYBRID

Answer 15

observation of 2 alleles

Question 16

WHAT IS THE MEANING OF PHENOCOPY?

Answer 16

non-genetic, non-heritable, outer environment causes one genotype to look like another genotype

EG: woman dyes her hair from brown to black, looks like a different genotype, but her children will inherit brown hair

Question 17

DEFINE PENETRATION

Answer 17

determines the probability that the allele will be expressed in the phenotype

Question 18

WHAT IS THE IDENTITY OF RECIPRICAL CROSSES?

Answer 18

inheritance of autosomal genes is not dependent on sex

Question 19

DEFINE DOMINANT RECESSIVE

Answer 19

dominant allele completely masks the expression of recessive allele

Question 20

DEFINE CODOMINANCE

Answer 20

phenotype will express both alleles independent to each other (e.g. blood: allele A + allele B = blood type AB)

Question 21

DEFINE INCOMPLETE DOMINANCE

Answer 21

–will express both phenotypes of both alleles, phenotype is an intermediate between the
dominant and recessive homozygotes (dominant blue + recessive red = purple flower)

Question 22

NAME THE 3 LEVELS WHICH ALLELES CAN EFFECT

Answer 22

a) whole organisms - complete dominance, heterozygote looks like a homozygote
(round seed shape vs. wrinkled seed shape)

b) cell – incomplete dominance, we can distinguish individual cells
(low osmotic pressure vs. high osmotic pressure )

c) molecule - codominance, 50 % dominant and 50 % recessive allele
(functional enzyme vs. defective form of an enzyme)

Question 23

WHO DOES MENDELS LAWS NOT APPLY TO?

Answer 23

does not apply to asexual or haploid organisms

Question 24

WHAT IS MENDELS FIRST LAW?

Answer 24

Uniformity of F1 generation
-if you cross two homozygotes (AA x aa) → all individuals in F1 are equal (Aa)

Question 25

WHAT IS MENDELS SECOND LAW?

Answer 25

Principle of segregation -two alleles in one gene separate from each other into two gametes, each carrying one allele -refers to F2 DOMINANT RECESSIVE -phenotype: 3.1 -genotype: 1.2.1 INTERMEDIATE & CODOMINANCE -phenotype: 1.2.1 -genotype: 1.2.1

Question 26

WHAT IS MENDELS THIRD LAW?

Answer 26

Independent assortment -alleles of two or more genes assort independently of one another

Question 27

WHAT IS THE DIHYBRID F2 GENERATION?

Answer 27

P = AABB x aabb or AAbb x aaBB F1 = in both cases: AaBb (all uniform)→ 4 times F2 = AaBb x AaBb → Punnett square GENOTYPES = genotypes: 9 different genotypes (1:2:1:2:4:2:1:2:1 → (1:2:1)^2 ) PHENOTYPES = 4 different phenotype (ratio 9:3:3:1 → (3:1)^2 )

Question 28

WHAT IS AN ANALYTICAL BACKCROSS?

Answer 28

AaBb x aabb -B1: 1:1:1:1

Question 29

WHAT IS A POLYHYBRID CROSS?

Answer 29

more than 2 genes observed -number of gametes = 2^n -number of zygotes = 4^n -genotype = (1:2:1)^n -phenotype = (3:1)^n

Question 30

NAME SOME DIFFERENCES FROM MENDELS LAW

Answer 30

lethality, decreased vitality sex linked heredity decreased penetrance different expressivity gene linkage gene interactions mitochondrial heredity polygenic heredity gene imprinting dynamic mutations structural balance chromosomal aberrations

Question 31

WHAT DOES LETHALITY / DECREASED VITALITY MEAN?

Answer 31

not all genotypes have the same variability COMPLETE RECESSIVE LETHALITY -recessive and dominant homozygotes are lethal -1AA : 2Aa:1aa (dead) or 1AA (dead) : 2Aa : aa COMPLETE DOMINANT LETHALITY -dominant homozygote and heterozygote are lethal -caused by a mutation which is not passed onto next generation -1AA (dead) : 2Aa (dead) : 1aa DECREASED VITALITY RECESSIVE -affect dominant or recessive homozygotes -1AA : 2Aa : 1aa (sick) or 1AA (sick) : 2Aa : 1aa DECREASED VITALITY DOMINANT -affects dominant or recessive homozygote + heterozygote -1AA : 2Aa (sick) :1aa (sick) or 1AA (sick): 2Aa (sick):1aa

Question 32

WHAT IS MORGANS FIRST LAW?

Answer 32

genes are in a linear order on chromosomes

Question 33

WHAT IS MORGANS SECOND LAW?

Answer 33

genes of a chromosome form a linkage group -number of linkage groups is equal to the number of pairs of homologous chromosomes

Question 34

WHAT IS MORGANS THIRD LAW?

Answer 34

Genes of homologous paired chromosomes can undergo crossing-over and gene exchange -frequency of crossing over is directly proportional to the distance between genes (in centimorgans cM) -distance of 1cM means 1% frequency of recombination during crossing over

Question 35

HOW MANY GENES DETERMINE THE ABO BLOOD GROUP OF HUMANS?

Answer 35

1

Question 36

WHERE CAN YOU FIND ANTIGENS AND ANTIBODIES?

Answer 36

antigens = surface of erythrocytes antibodies = in plasma -antigen produced from precursor polysaccharide and enzyme H adds another polysaccharide = H antigen (blood group O) -from H antigen A and B antigens can be formed

Question 37

WHAT IS THE FREQUENCY OF BLOOD GROUPS?

Answer 37

0 > A > B > AB

Question 38

WHICH BLOOD GROUP IS THE UNIVERSAL DONOR?

Answer 38

O

Question 39

WHICH BLOOD GROUP IS THE UNIVERSAL ACCEPTOR?

Answer 39

AB

Question 40

WHY CANT ANTIGENS MIX WITH WITH THEIR ANTIBODY? eg; A antigen and anti-A antibody

Answer 40

antigens are similar to bacterial saccharides to which antibodies react, therefore they cannot mix

Question 41

WHAT IS THE RHESUS FACTOR?

Answer 41

a certain type of protein found on the outside of blood cells -genetically inherited from mother -mainly influences antigen D -dominant: Rh+ (83%) -recessive: Rh- (17%) Rh- can donate to Rh+ → Rh+ can accept Rh- and Rh+ Rh+ can not donate to Rh- → Rh- can only accept Rh- problem during 2nd pregnancy: -Rh- mother and Rh+ child -body of mother from the 1st pregnancy has antibodies against Rh, which it now used against the child in the womb. -antibodies in a pregnant woman's blood destroy her baby's blood cells

Question 42

HOW MANY GAMETES DOES A TRIHYBRID CROSS FORM?

Answer 42

8

Question 43

THE PRODUCT AND SUM RULE OF MENDELIAN GENETICS

Answer 43