Genetic Inheritance

Question 1

Genes

Answer 1

Segments of DNA in a chromosome

Question 2

Locus (Loci)

Answer 2

A specific place where a gene is located

Question 3

Chromatid

Answer 3

One of two identical copies of a chromosome

Question 4

Centromere

Answer 4

Connects identical sister chromatids

Question 5

Telomere

Answer 5

A region at the ed of a chromosome for stability

Question 6

Typical human diploid cells have ___ pairs of chromosomes - a total of ___

22 pairs are called ____

And the 23rd pair is ___ or ___

Answer 6

23 , 46

Autosomal

XX or XY

Question 7

Human somatic cells are _____

Answer 7

Diploid cells that are differentiated

Question 8

What cells are haploid?

Answer 8

Gametes

Question 9

_______ cells are cells that are undifferentiated and can divide into two _________ cells

Answer 9

Stem, diploid

Question 10

Refer to pairs of chromosomes

Answer 10

Homologous chromosomes

Question 11

Karyotype

Answer 11

Entire set of a person’s chromosomes. 46 chromosomes show in the karyotype of each of the patient’s cells

Question 12

Mosaicism

Answer 12

A condition in which cells from a patient have different genotypes (and karyotype)

Question 13

Downs Syndrome

Answer 13

Some 46XX, some 47XX, +21

Question 14

Klinefelter Syndrome

Answer 14

Some 46XY, some 47XXY

Question 15

Turner Syndrome

Answer 15

Some 46XX, some 45XO

Question 16

Lionization

Answer 16

X inactivation - the choice of which x -chromosome to be inactivated is random

Question 17

Ovaries and testes undergo ________ to produce ________ that have one of each pair of chromosomes and are called _________ cells

Answer 17

Meiosis ; gametes ; haploid

Question 18

Interphase

Answer 18

Chromosome duplication

Question 19

Cell division

Answer 19

One copy of each chromosome and 1/2 of the cytoplasm/organelles are distributed b/w the 2 daughter cells

Question 20

Homologous recombination

Answer 20

Can produce new combos of genes in meiosis; homologous chromosomes are not identical

Question 21

Non-disjunction

Answer 21

The failure of one or more pairs of homologous chromosomes, or SISTER CHROMATIDS to separate normally during division

Question 22

Meiosis consists of __ round(s) of DNA ________ and __ round(s) of nuclear __________

Answer 22

1 ; replication

2 ; divisions

Question 23

Autosomal

Answer 23

Chromosomes common in both genders, one from each parent

Question 24

Sex chromosomes

Answer 24

X, female

Y, male

Question 25

Name two ways that meiosis creates genetic diversity.

Answer 25

1) Random segregation of homologs

2) Cross-over exchange

Question 26

Nondisjunction

Answer 26

When homologs fail to separate properly

Common and increases w/ advancing maternal age

Cause of spontaneous abortions and mental retardation

Question 27

Aneuploid

Answer 27

Cells with abnormal chromosome number

Trisomy 21 (Down Syndrome): most common cause of mental retardation

In 90% of trisomy 21 patients, the additional chromosome is maternal
70% occur during MI
30% occur during MII

Question 28

Euploid

Answer 28

Cells with a normal number of chromosomes

Question 29

Genotype vs. phenotype

Answer 29

An individual’s genetic makeup vs. what is actually observed

Question 30

Autosomal Dominant Inheritance

Answer 30

• Only 1 allele of a gene is needed for expression
• Affected offspring has one affected parent
• Males and females can transmit trait to both males and females
• Recurrent risk is 50%

Ex) Postaxial polydactyly

Question 31

Autosomal Recessive Inheritance

Answer 31

2 copies of a gene is needed to influence phenotype

Recurrent risk for heterozygous parents is 25%

Ex) tyrosinase-negative albinism

Question 32

X-linked Recessive

Answer 32

Because males have one X, disease Allen on X in males is termed “hemizygous”

No such thing as a male carrier - they have it or they don’t

Females can be heterozygous carriers though

Ex) Duchenne Muscular Dystrophy

Question 33

X-Linked Dominant

Answer 33

Very rare, no carriers

Males with the disease
Males transmit the trait only to females - 100% transmission

Females with the disease transmit the trait to both males and females-50% of offspring

Ex) hypophophatemia

Question 34

The frequency a gene manifest itself is called ________

Answer 34

Penetrance

Question 35

Reduced Penetrance

Answer 35

In some cases, 100% of individuals inheriting a genetic defect show the clinical presentation (phenotype) of the disease (100?% penetrance)

In other cases penetrance is less than 100%

Ex) Retinoblastoma (autosomal dominant inheritance): phenotype occurs in 90% of individuals inheriting gene defect, so 90% penetrance

Question 36

Variable Expressivity

Answer 36

Term used to describe the range of phenotype that vary b/w individual w/ a specific genotype

Ex) Neurofibromatosis
Pts develop tumor-like growths called neurofibromas and develope cafe-au-lait spots

Question 37

Locus heterogeneity

Answer 37

Single disorder, trait or pattern of traits caused by mutations in genes at different chromosomes loci

Ex) Osteogenesis imperfecta

  - brittle-bone disease
  - mutations in collagen genes

Question 38

Probability

Answer 38

Defined as the proportion of times that a specific outcome occurs in a series of events - b/w 0 and 1

Question 39

What is the probability of producing three girls? (THe probability of producing 1 girl is 1/2)

Answer 39

1/2 x 1/2 x 1/2 = 1/8

Question 40

What is the probability of producing either three girls or three boys?

Answer 40

1/8 + 1/8 = 1/4

Question 41

______ specify the proportions of each allele in a population

Answer 41

Gene frequencies

Question 42

________ specify the proportions of each genotype in a population

Answer 42

Genotype frequencies

Question 43

Hardy-Weinberg Principle

Answer 43

P^2 + q^2 + 2pq = 1

Specifies the relationship b/w gene frequencies and genotype frequencies
Useful in estimation genes frequencies from disease prevalence data and in estimating the incidence of heterozygous carriers of recessive disease genes

Question 44

Autosomal Dominant Inheritance

Answer 44

Characterized by vertical transmission of the disease phenotype, lack of skipped generations, and roughly equal numbers of affected males and females

Question 45

Autosomal Recessive Inheritance

Answer 45

Characterized by clustering of the disease phenotype among siblings,but the disease is not typically seen among parents or other ancestors. Equal numbers of males and females and consanguinity may be present

Question 46

Consanguineous makings are more likely to produce offspring affected by rare __________ Disorders

Answer 46

Autosomal Recessive

Question 47

Studies show that mortality rates among the offspring of _______ matings are up to 9% higher than those of the general population

Answer 47

First-cousin

Question 48

Each person carries one to five ________ lethal to offspring if matched with another copy of the mutation (homozygosity)

Answer 48

Recessive mutations

Question 49

Traits in which variation is thought to be caused by the combined effects of multiple genes are called ________

Answer 49

Polygenic genes

Question 50

When environmental factors cause variation in the trait, the term ________ is used

Answer 50

Multifactorial

Question 51

Liability distribution

Answer 51

Seen in diseases that do not follow the bell-curve distribution

Question 52

For multifactorial diseases that are either present or absent, it is thought that a ____________ use be crossed before the disease is expressed

Answer 52

Threshold liability

Question 53

Pyloric Stenosis

5x more common in _______ than ________

Answer 53

Muscular hypertrophy b/w stomach and duodenum leading to vomiting and obstruction

Males than females

Males need less risk genes to show disease

Least affected sex has a higher risk threshold and transmits the condition more often to the most frequently affected sex

Question 54

Multifactorial disease

Answer 54

Caused by the simultaneous influence of multiple genetic and environmental factors