chapter fifteen

Question 1

chromosome theory of inheritance

Answer 1

• Mendelian “factors” - genes
• specific loci on chromosomes
• replicated, segregated, independently assorted

Question 2

Thomas Hunt Morgan

Answer 2

provided first solid evidence for chromosome theory of inheritance
- fly lab

Question 3

what did Morgan use in his research

Answer 3

Drosophila melanogaster
- has 4 pairs of chromosomes

Question 4

mutant phenotype of Drosophila melanogaster

Answer 4

white eyes
- alternate to wild type, originated as mutation

Question 5

wild type of Drosophila melanogaster

Answer 5

red eyes

Question 6

wild type

Answer 6

most commonly observed in natural populations
- could be dominant or recessive

Question 7

white-eye x wild cross

Answer 7

F1: all red eyes (wild type)
F2: all females red eyes, 50% males red, 50% males white

Question 8

sex-linked genes

Answer 8

a gene located on either sex chromosome
- X or Y linked

Question 9

linked genes

Answer 9

• not sex-linked
• physically linked to other, located near each other and inherited together in genetic crosses
• don’t assort independently

Question 10

what are genetic recombinations a result of?

Answer 10

independent assortment of chromosomes, crossing over, which sperm fertilizes which egg

Question 11

sex determination of mammals

Answer 11

XX, XY
- depends on if sperm has X or Y
- male has Y

Question 12

sex determination of Drosophila

Answer 12

X:autosome ratio determines male/female
- X/a < 0.5 = male
- X/a > 1 = female
- between 0.5-1 = intersex

Question 13

sex determination of some insects

Answer 13

• females XX
• males XO
• determined if sperm contains X chromosome or not

Question 14

sex determination of birds, some fish/insects

Answer 14

• ZW female
• ZZ male

Question 15

sex determination of bees and ants

Answer 15

• diploid - females develop from fertilized eggs
• haploid - males develop from unfertilized eggs

Question 16

potential problem for males in transmission of X-linked recessive traits

Answer 16

any male receiving recessive allele from mother will express the trait because they have 1 X chromosome

Question 17

why don’t recessive lethals don’t normally appear in females

Answer 17

• they have another X chromosome, dominant masks recessive
• would need 2 copies of recessive, and would only get this from dad, but if dad had it he wouldn’t survive

Question 18

ex. of recessive sex-linked traits

Answer 18

• Red-green color blindness
• Duchenne Muscular Dystrophy
• Hemophilia

Question 19

X-inactivation

Answer 19

• almost all of one X chromosome becomes inactivated during early embryonic development, condenses into
  Barr Body
• involves modification of DNA/proteins, attaches methyl groups to nucleotides

Question 20

Barr Body

Answer 20

inactivated X chromosome that lies inside of nuclear envelope
- reactivated in cells that give rise to eggs

Question 21

nondisjunction

Answer 21

when members of a pair of homologous chromosomes don’t move properly apart during meiosis I

Question 22

disjunction

Answer 22

sister chromatids fail to separate in meiosis II
- 1 gamete receives 2 of same type of chromosome, other receives no copy

Question 23

aneuploidy

Answer 23

when aberrant gamete unites w/ normal at fertilization, zygote will have abnormal # of particular chromosome

Question 24

trisomic

Answer 24

if chromosome is present in triplicate in zygote
- 2n + 1

Question 25

monosomic

Answer 25

fertilization involving gamete w/ no copy (missing chromosome) in zygote - 2n - 1

Question 26

polyploidy

Answer 26

having an unusual number of complete chromosome sets in somatic cells - triploidy - tetraploidy

Question 27

where is polyploidy common?

Answer 27

plants

Question 28

where is polyploidy rare?

Answer 28

animals - but more normal in appearance than aneuploids

Question 29

types of alterations in chromosome structure

Answer 29

1. deletions 2. duplication 3. inversion 4. translocation

Question 30

deletions

Answer 30

chromosomal fragment lost - then misses certain genes

Question 31

duplication

Answer 31

broken fragment may become reattached as extra segment to a sister/nonsister chromatid

Question 32

inversion

Answer 32

chromosomal fragment may reattach to original chromosome but in reverse orientation

Question 33

translocation

Answer 33

chromosomal fragment joins non homologous chromosome

Question 34

down syndrome (Trisomy 21)

Answer 34

- extra chromosome 21, 47 chromosomes - short stature, heart defects, developmental delays, shorter life span - incidence increases with age of parent

Question 35

ex. of aneuploidy of sex chromosomes

Answer 35

1. Klinefelter's syndrome 2. XYY 3. Trisomy X 4. Turner's syndrome

Question 36

Klinefelter's syndrome

Answer 36

- XXY - have male sex organs but testes are small and produce little/no sperm - male

Question 37

XYY

Answer 37

typical sexual development, taller than average - male

Question 38

Trisomy X

Answer 38

- female - taller than average, but at risk for learning disabilities

Question 39

Turner's syndrome

Answer 39

- monosomy X - sterile, sex organs don't mature, demonstrate sex characteristics when provided w/ estrogen - female

Question 40

extra-nuclear (organelle) genes

Answer 40

- genes located in organelles - mitochondria/chloroplasts

Question 41

mitochondrial myopathy

Answer 41

- weakness, intolerance of exercise, muscle deterioration - defect in genes of mitochondria that reduce amount of ATP made in ETC/synthase

Question 42

what is now being used to trace ancestry?

Answer 42

MtDNA

Question 43

where are mitochondrial disorders inherited from?

Answer 43

mother

Question 44

types of autosomal aneuplodies in humans

Answer 44

1. trisomy 21 - Down syndrome 2. trisomy 18 - Edward syndrome 3. trisomy 13 - Pateau syndrome - all other types end in miscarriage