Chapter 11

Question 1

Why do linked genes not show independent assortment?

Answer 1

Because two recombinant gametes can result from crossing over between the homologous chromosomes when paired in prophase I

Question 2

What’s the difference between parental and recombinant phenotypes?

Answer 2

Parental are the ones that inherit the chromosomes that were not involved in recombination in the dihybrid parent
Recombinant can only occur from crossing over

Question 3

What is the minimum to maximum recombinant frequency possibilities?

Answer 3

1% to 50%

Question 4

How do you find the frequency percentage of the recombinants?

Answer 4

Divide the number of recombinants by the total progeny and multiply that by 100

Question 5

What is the unit of a linkage map?

Answer 5

Map unit (mu)
Also called the centimorgan (cM)
It is equal to the frequency percentage

Question 6

what type of cross is used to see if two genes are linked or not?

Answer 6

Test cross

Question 7

What is a linkage map?

Answer 7

A map of a chromosome that shows the distance (map units) two or more genes on the same chromosome are apart

Question 8

What are sex-linked genes?

Answer 8

Genes located on the sex chromosomes (one or more pairs per person)

Question 9

What are autosomes?

Answer 9

Any other chromosome other than sex chromosomes

Question 10

Why is the sex determining gene on the Y chromosome?

Answer 10

The SRY gene

Master switch that directed development toward maleness at an early point in embryonic development

Question 11

When does the SRY gene become active in sex determination in the embryo?

Answer 11

After 6-8 weeks

Question 12

What is a wild type allele and what’s it’s notation?

Answer 12

A normal genotype where any change from wild type is a mutant

Add a subscripted + to the allele to show its a wild type

Can be recessive or dominant alleles

Question 13

What is a pedigree chart?

How are males and females represented?

Answer 13

A chart that shows all parents and offspring for as many generations as possible
Includes sex and trait of interest

Males- square
Females- circle

Question 14

What is a Barr body?

Answer 14

The inactive, condensed X chromosome in the nucleus as a dense mass of chromatin

Question 15

How do you determine if a given gene is sex linked or not?

Answer 15

If it is sex linked you will get difference ratios since the male can only carry one allele on its X chromosome

Question 16

What are the four major forms of chromosome alterations after breakages?

Answer 16

1. Deletion occurs if a corker segment is lost
2. Duplication occurs if a broken segment is inserted into the homologous chromosome
3. Translocation occurs if a broken segment is attached to a different chromosome
4. Inversion occurs if a broken segment is reattached to the same place but in reverse

Question 17

What is nondisjunction or misdivision?

What do these result in?

Answer 17

Nondis- The failure of homologous pairs to separate during the first meiotic division
Mis- the failure of chromatids to separate during the second meiotic division

Results in a loss or gain of whole chromosomes (aneuploids)

Question 18

Aneuploids vs euploids vs polyploids?

Answer 18

Aneuploids- individual with extra or missing chromosomes
Euploids- normal sets of chromosomes
Polyploids- individuals that receive one or more extra copies of the entire haploid complement of chromosomes

Question 19

How does Down syndrome occur?

Answer 19

Nondisjunction or misdivision of chromosome 21

Question 20

How are polyploids formed?

Answer 20

Failure of spindle to function normally during mitosis

Fails to separate duplicated chromosomes

Question 21

What is autosomal recessive inheritance?

Answer 21

A pattern in which individuals who are homozygous for the dominant allele are free of symptoms and are not carriers while those homozygous recessive show the trait

Question 22

What is autosomal dominant inheritance?

Answer 22

The allele that causes he trait is dominant
(Most often cases)
Homozygous recessive people are unaffected

Question 23

What is X-linked recessive inheritance?

Answer 23

Traits due to inheritance of recessive alleles carried on the X chromosome

Question 24

What is genetic counselling?

Answer 24

Allows prospective parent to assess the possibility that they might have an affected Child.
It begins with identification of parental genotypes through pedigrees and works it’s way down

Question 25

What is prenatal diagnosis?

Answer 25

Where cells derived from a developing embryo or its surrounding tissues are tested for the presence of mutant alleles or chromosomal alterations

Question 26

What is amniocentesis?

Answer 26

Cells are obtained from the amniotic fluid (water surrounding embryo in mothers uterus) to test for genetic faults

Question 27

What is chorionic villus sampling?

Answer 27

Cells are obtained from portions of the placenta that develop from tissues of the embryo to test for genetic faults

Question 28

How are inherited disorders detected before symptoms arise?

Answer 28

Genetic screening

Question 29

What is cytoplasmic inheritance?

Answer 29

The pattern of inheritance follows that of genes in the cytoplasmic organelles (mitochondria and chloroplasts)

Question 30

Do you have more of your fathers DNA or mothers? Why?

Answer 30

Mothers since the mitochondria’s DNA is all from your mother

Question 31

What is genomic imprinting?

Answer 31

The expression of an allele of a particular nuclear gene is based on whether an individual organism inherits the allele from the male or female parent

Question 32

What is the phenomenon “loss of printing”?

Answer 32

Where the imprinting mechanism for a gene does not work