Chapter 10

Question 1

Gregor Johann Mendel

Answer 1

father of modern genetics; quantitatively analyzed garden peas

Question 2

why did he study peas?

Answer 2

Greg or Mandel performed experiments with garden peas because there are many varieties available with easily distinguishable traits that can be quantified; they are small, easy to grow, and produce large numbers of off spring quickly; their reproductive organs can be easily manipulated so that pollination can be controlled, they can self fertilize

Question 3

what is true breeding/homozygous?

Answer 3

plants that have been self fertilized for several generations; each variety contained only one type of trait

Question 4

genotype

Answer 4

genetic make up

Question 5

phenotype

Answer 5

external appearance

Question 6

what is characteristic?

Answer 6

heritable features

Question 7

what is trait?

Answer 7

alternative forms of character

Question 8

when is a trait considered dominant?

Answer 8

trait expressed in the F1 generation; Purple

Question 9

when is a trait. considered recessive?

Answer 9

trait not expressed in the F1 generation; white

Question 10

what is an F1 and F2 generation?

Answer 10

Mendel had a specific experimental design: he first established true breeding varieties by allowing plants to self fertilize for several generations, he ensured that each variety contained only one type of trait. He named these parental lines the P generation. he then crossed two varieties exhibiting alternative traits. He named the resulting offspring the F1 generation. He then allowed the plants from the F1 generation to self fertilize. He named the offspring the F2 generation.

Question 11

what Mindel observed

Answer 11

Mindel counted the number of each type of plant in the F2 generation. He found a consistent proportion in expressed traits for his different crosses. Three fourths of the F2 individuals expressed the dominant trait while one fourth express the recessive trait. The dominant: recessive ratio among the F2 plants was always close to three: one.

Question 12

what Mindel observed

Answer 12

Mindel reasoned that the recessive trait must somehow be hidden in the F1 generation but just not expressed. He allowed the F2 to self fertilize and form the F3 generation. He found that one fourth of the plants from the F2 that were recessive were true breeding in the F3. He found that the three –fourths of the plants from the F2 that were dominant: only one –third were true breeding in the F3. The remaining two– thirds showed both traits.

Question 13

what Mindel observed

Answer 13

he determined that the ratio of three: one that he observed in the F2 generation was in fact a disguised 1:2:1 ratio (True breeding dominant: not true breeding dominant: true breeding recessive:

Question 14

Mendel proposes a theory

Answer 14

hypothesis one: parents don’t transmit traits directly to their offspring. Parents transmit information about the trade in the form of what Mindel called Factors.

hypothesis 2: each parent contains two copies of the factor governing each trait. The two copies of the factor may or may not be the same. Homozygous individuals have 2 similar copies. Heterozygous individuals have two different copies.

Question 15

Mendels laws

Answer 15

Mendel’s first law: segregation: the two alleles of a trait separate from each other during the formation of gametes,so that half of the gametes will carry one copy and half will carry the other copy

Mendel’s 2nd law: independent assortment: genes located on different chromosomes are inherited independently of one another

Question 16

polygenic

Answer 16

several genes affect one character; for example, height in humans

Question 17

pleiotropic effects

Answer 17

an allele that has more than one effect on the phenotype is considered pleiotropic – one gene affects many characters. these effects are characteristic of many inherited disorder, such as cystic fibrosis and sickle cell anemia.

Question 18

pleiotropic affects of the cystic fibrosis gene

Answer 18

defective CF gene produces faulty chloride transport channels – causing mucus to build up in The liver, pancreas, lungs, sweat glands.

Question 19

incomplete dominance

Answer 19

not all alternative alleles are either fully dominant or fully recessive in heterozygotes. In such cases, the alleles exhibit incomplete dominance and produce a heterozygous phenotype but is intermediate between those of the parents. For example, crossfertilizing a red flower with A white flour will result in a pink flower.

Question 20

environmental effects

Answer 20

The degree to which many alleles are expressed depends on the environment. for example: some alleles are heat – sensitive. Arctic foxes only produce for a pigment when temperatures are warm. The CH allele in Himalayan rabbits and Siamese cats encodes a heat – sensitive enzyme, called tyrosinase, that that controls pigment production. tyrosinase is in active at high temperatures.

Question 21

Epistasis

Answer 21

in some situations, two or more genes interact with each other, such that one gene contributes to or masks the expression of the other gene. In epistasis, one gene modifies a phenotypic expression produced by the other. For example, in corn, to produce and deposit pigment, a plant must possess at least one functional copy of each of two genes. One gene controls pigment deposition. The other Gene controls pigment production.

Question 22

how epistasis affects corn kernel color

Answer 22

white (AAbb) and white (aaBB) are crossfertilized to form F1 generation purple (AaBb) which is then cross fertilized with a female AaBb. It produces 9/16 purple and 7/16 white. You need to have both a dominant A gene and dominant B gene in order to have purple kernels.

Question 23

The effect of epistasis interactions on coat color in dogs

Answer 23

no dark pigment in for: yellow lab

eebb– Yellow fur; brown nose, lips, Eye rims
eeB_-gold fur: Black nose, lips, Eye rims
E_bb-Brown fur, nose, lips, eye rims
E_B_-Black fur, nose, lips, eye rims

Question 24

codominance

Answer 24

A gene may have more than two alleles in a population. Often, in heterozygotes, there’s not a dominant allele but, instead, both alleles are expressed. These alleles are said to be codominant. for example, spotted or Roan offspring or human blood groups.

Question 25

what is heredity?

Answer 25

heredity is the tendency for traits to be passed from parent to offspring

Question 26

co dominance: human blood type

Answer 26

The gene that determines ABO blood type in humans exhibits more than one dominant allele. The gene encodes an enzyme that adds sugars to lipids are the membranes of RBCs. These sugars act as recognition markers for cells in the immune system kind of like surface proteins in plasma membranes. The gene that encodes the enzyme designated I, has a three alleles: IA, IB, and I. different combinations of the three alleles produce for different phenotypes, or blood types – A, B, AB, and O. A B can accept from most people. O can’t accept from most people.

Question 27

human chromosomes

Answer 27

each human somatic cell normally has 46 chromosomes, which in meiosis form 23 pairs. 22 of the 23 pairs are perfectly matched in both males and females that are called autosomes. One pair are the sex chromosomes. Females are designated XX, while males are designated XY. Some of the genes on the Y chromosome are responsible for malenessfor example testes, sperm, preposterous amounts of testosterone.

Question 28

genetic disorders

Answer 28

sometimes errors occurred during meiosis. Nondisjunction is the failure of chromosomes to separate correctly during meiosis one or meiosis two. This leads to aneuploidy, On abnormal chromosome number. Most of these abnormalities cause of failure to develop or early death before adulthood. In contrast, individuals with an extra copy of chromosome 21 or, more rarely, chromosome 22 can survive to adulthood. however, these individuals have to latest development and mental impairment. Down syndrome is caused by having an extra copy of chromosome 21.

Question 29

trisomy

Answer 29

have one more chromosome in your cells than you’re supposed to have. so three chromosomes in one cell. trisomy those unnatural with life will be naturally miscarried. For example, trisomy 18.

Question 30

Monosomy

Answer 30

having one less chromosome in your cell than you’re supposed to have. so one chromosome.

Question 31

nondisjunction may also affect the sex chromosomes. Nondisjunction of the X chromosome creates three possible viable conditions.

Answer 31

XXX female: Usually taller than average but other symptoms vary; XXY male (Klinefelter syndrome): sterile male with many female featuresand diminished mental capacity; XO female (turner syndrome):sterile female with webbed neck and diminished stature; OY (nonviable): intercell mass/not implant and uterus

Question 32

accidental changes in genes are called mutations.

Answer 32

mutations occur only rarely and almost always result in recessive alleles. Not eliminated from the population because they are not usually expressed in most individuals(heterozygotes); in some cases, particularly mutant alleles have become more common in human populations and produce harmful effects call genetic disorders.

Question 33

hemophilia: sex linked trait

Answer 33

hemophilia is a blood clot in disorder. Some forms of hemophilia is excellent.

Question 34

sickle cell disease: recessive trait

Answer 34

sickle cell disease or anemia is a recessive hereditary disorder. Affected individuals are homozygous recessive and carry a mutated gene that produces a defective version of hemoglobin. The hemoglobin sticks together inappropriately and produces a stiff red blood cell with a sickle shape. The cells cannot move through the blood vessels easily and tend to form clots. This causes sufferers to have intermittent illnesses and shortened lifespans. both parents have to be carriers.

Question 35

tay-Sachs disease: recessive trait

Answer 35

tay-Sachs disease is another disease caused by a recessive allele. Incurable disorder in which the brain deteriorates. Sufferers (those homozygous for the recessive allele) rarely live beyond the five years of age.

Question 36

genetic counseling can help identify parents who are at risk of producing children with genetic defects and assess the genetics state of early embryos

Answer 36

genetic counselors utilize genetic screening. Amniocentesis is when amniotic fluid is sampled and isolated fetal cells are then grown in culture and analyzed. preterm labor and miscarriage is a risk. Chorionic villa sampling is when the fetal cells from the chorion in the placenta are removed for analysis.

Question 37

genetic counselors look at three things from the cell cultures obtained from either amniocentesis or Chorionic villus sampling.

Answer 37

chromosomal Karyotype: Analysis can reveal aneuploidy or gross chromosomal alterations. enzyme activity: in some cases, it’s possible to test directly for the proper functioning of enzymes associated with genetic disorders. Genetic markers: test for the presence of mutations at the same place on chromosomes where disorder causing mutations are found.