Chapter 15: Chromosomal Inheritance

Question 1

Why did Morgan study Drosophila melanogaster?

Answer 1

1. They produce many offspring
2. A generation can be bred every two weeks
3. They only have four pairs of chromosomes

Question 2

Wild type

Answer 2

Normal phenotype

More common

Question 3

What was the key to the development of the chromosome theory of inheritance?

Answer 3

Morgan’s discovery of a trait that correlated with the sex of flies

Only males had white eyes

Question 4

SRY

Answer 4

Sex determining region on the Y

Responsible for development of the testes in an embryo

Question 5

Common x-linked recessive disorders

Answer 5

Color blindless

Muscular dystrophy

Hemophilia

Question 6

Barr body

Answer 6

Only one of two x chromosomes is used

The inactivated x chromsome condenses into a Barr body

Question 7

Linked genes

Answer 7

Genes located on the same chromsome that tend to be inherited together

Question 8

What did morgan find about linked genes?

Answer 8

Body color and wing size are usually inherited together

Question 9

Genetic recombination

Answer 9

The production of offspring with combinations of traits differing from either parent

Question 10

When is a 50% frequency of recombination observed?

Answer 10

Any two genes on different chromosomes

Question 11

Variation factors

Answer 11

Recombinant chromosomes (caused by crossing over)

Random fertilization

All increases genetic variation with natural selection works upon

Question 12

Genetic map

Answer 12

Ordered list of the genetic loci along a particular chromosome

Question 13

What did Sturtevant predict?

Answer 13

The farther apart two genes are, the higher the probability that crossing over will occur and therefore have a higher recombination frequency

Question 14

Map units

Answer 14

Distance between genes

Centimorgan or map unit=1% recomonbination frequency

Question 15

How did Sturtevant find linkage groups?

Answer 15

Saw that genes clustered into four groups of linked genes

Provided additional evidence that genes are on chromosomes

Question 16

Plants and genetic changes

Answer 16

They tolerate them much better than animals

Question 17

Nondisjunction

Answer 17

Pairs of homologous chromosomes do not separate normally during meiosis

Question 18

Aneuploidy

Answer 18

Results from the fertilization of gametes in which nondisjunction occurred

All offspring do not have the correct number of a particular chromsome

Question 19

Monosomic

Answer 19

Zygote has only one copy of a particular chromosome

Question 20

Trisomic

Answer 20

Zygote has three copies of particular chromsome

Question 21

Polyploidy

Answer 21

Condition in which an organism had more than two complete sets of chromosomes

Ex: Triploidy and tetreploidy

Polyploids are common in plants

More normal in appearance than aneuploidy

Question 22

Deletion

Answer 22

Removes a chromosomal segment

Question 23

Duplication

Answer 23

Repeats a segment

Question 24

Inversion

Answer 24

Reverses orientation of a segment within a chromosome

Question 25

Translocation

Answer 25

Moves a segment from one chromosome to another

Question 26

Syndrome

Answer 26

a specific set of symptoms

Question 27

Down syndrome

Answer 27

An aneuploid condition that results from three chromsome 21s

Question 28

XXX females

Answer 28

Aneuploids Completely healthy

Question 29

Klinefelter syndrome

Answer 29

XXY extra chromosome in males

Question 30

XO females

Answer 30

Turner syndrome (monosomy x) Females are sterile

Question 31

What is the only viable monosomy?

Answer 31

X0 45-X Turner syndrome

Question 32

Translocations of chromsomes...

Answer 32

can cause certian cancers

Question 33

Two execptions to normal Mendelian genetics

Answer 33

1. Chromosomes located in the nucleus | 2. Genes located outside the nucleus

Question 34

Genomic imprinting

Answer 34

Silencing of certain genes depending on which parent passes them on Result of methylation (CH3)

Question 35

Result of methylation

Answer 35

Genomic imprinting

Question 36

What is important about genomic imprinting?

Answer 36

Has to be reversible so you dont have individuals with completely silenced genes after meiosis

Question 37

Extranuclear genes

Answer 37

Found in organelles Ex: mitochondria and chloroplasts

Question 38

How are extranuclear genes inherited?

Answer 38

Maternally Zygote's cytoplasm comes from the egg

Question 39

First evidence of extranuclear genes

Answer 39

Patches of color on leaves Chloroplast genes

Question 40

Defects in mitochondrial genes

Answer 40

Can prevent cells from making enough ATP Affects muscular and nervous systems

Question 41

Autosomal genes

Answer 41

Regular chromosomes Not sex linked or anything

Question 42

What do crossovers cause?

Answer 42

Recombination

Question 43

Why can't we use map units for physical distances?

Answer 43

Frequency of crossing over varies

Question 44

Philadelphia

Answer 44

Chromosome 22

Question 45

Where does down syndrome come from?

Answer 45

Nondisjunction in either parent in gamete cell production

Question 46

Theory of inheritance

Answer 46

Genes are at specific loci on the chromosome and in turn segregate during meiosis

Question 47

Non-reciprocal crossover

Answer 47

Deletion and duplication

Question 48

XIST gene

Answer 48

Activated only one x chromosome on females

Question 49

Inversion on chromsome

Answer 49

abnormal gametes may be found