Genetic Chapter 7 & 8

Phenotypic dimorphism

Phenotypic dimorphism

differentiation of sexes in animals is evident of this

Heteromorphic chromosomes

dissimilar ; chromosome pair with some homology but differing in size, shape, or staining properties

ex: sex chromosomes X and Y

Life cycles depend on ______ differentiation

sexual

Primary sexual differentiation

• before birth

involves only gonads where gametes are produced

Secondary sexual differentiation

• after birth

involves overall appearance of organism

Unisexual, dioecious, gonochoric

have only male or female reproductive organs

Bisexual, monoecious, hermaphroditic

have both male and female reproductive organs

• common in plants and animals

• produce both egg and sperm

Self Fertilization

• eggs fertilized by stored sperms

• majority produced are hermaphrodites ( both male and female reproductive organs)

• less than 1% offspring are males

• adults male mate w/ hermaphrodites

  • produce 1/2 male and 1/2 hermaphrodite offspring

Human Karyotype :

• 22 pairs of autosomal chromosome

• 1 pair of sex chromosome

  • 2 sex chromosomes

• normal human have 46 chromosomes

Klinefelter and Turner Syndromes

• 1940

• human abnormalities

• aberrant sexual development

• result from nondisjunction

  • X chromosome failed to segregate during meiosis

Klinefelter Syndrome XXY

• 47, XXY

• tall, long arms and legs

  • large hands and feet

• internal ducts are male, rudimentary testes fail to produce sperm

• feminine development not suppressed

  • enlarged breast, rounded hips

• abnormal social development

Turner Syndrome X

• 45, X

• phenotypically female

  • male external genitalia and internal ducts

  • ovaries are rudimentary

  • undeveloped breast

• short

• cognitive impairment

The human diploid number is

46 chromosomes

The karyotype for a Klinefelter individual

XXY

Which of the following human genetic conditions is missing a chromosome?

a. klinefelter syndrome

b. turner syndrome

c. down’s syndrome

b. turner syndrome

What is the ratio of male to female conceptions in a population called?

primary sex ratio

What is the ratio of male to female born in a population called?

secondary sex ratio

How many Barr bodies would one expect to see in cells of Turner syndrome females and Klinefelter syndrome males?

zero and one

Where is the general location of a barr body?

attached to the nuclear envelope

Which is not the tenant of the Lyon hypothesis?

a. X inactivation occurs early in development

b. X inactivation is passed down during mitosis

c. X inactivation occurs on the maternal X chromosome

d. initial X inactivation is random

c. X inactivation occurs on the maternal X chromosome

Female calico cats are an example of

Lyon hypothesis

The Y chromosome is genetically blank, however it has a gene that encodes for the protein

TDF

Members of diploid species normally contain ____ haploid sets

two

Mutations or aberrations

• variation from 2 haploid sets

• variation from the number of chromosomes

• rearrangement of genetic material within or among chromosomes

Aneuploidy

gain or loss of 1 or more chromosomes, but not a complete set

Euploidy

gain or loss of a complete haploid set

Polyploidy

• triploid - 3 sets

• tetraploid - 4 sets

3 or more sets

Monosomy

loss of 1 chromosome

2n - 1 ; 45

Trisomy

gain of 1 chromosome

2n + 1 ; 47

Tetrasomy

gain of 2 chromosome

2n + 2

Pentasomy

gain of 3 chromosomes

2n + 3

Autopolyploidy

multiples of the same genome

Allopolyploidy

multiples of closely related genomes

_______ resulting in monosomy and trisomy

nondisjunction

Monosomy 2n - 1

What is haploinsufficiency?

when 1 copy is not sufficient for organism to survive

Partial monosomy

part of a chromosome is lost

Autosome loss is not easily tolerated.

True or False

True

Cri-du-chat syndrome (cry of the cat

• 1/2 short arm of #5 is missing

• 46

• 5p (p arm is missing)

Trisomies for autosomes are often lethal

True or False

True

Autosomal Additions

• severe effects

• most lethal during development

• Down syndrome

  • trisomy 21

  • 47, 21+

  • nondisjunction of chromosome 21 during meiosis resulting in n + 1 gametes

• ovum most often is the source

Down Syndrome or Trisomy 21

• extra chromosome at #21

• 12 to 14 characteristics

• affected indicuduals express 6 to 8 on average

DSCR - Down Syndrome Critical Region

• critical region of chromosome 21

• genes are dosage sensitive

• responsible for many phenotypic associated syndromes

Origin of Extra Chromosome 21

• nondisjunction of #21 during meiosis

• homologs do not disjoin in anaphase I or II

  • lead to n+1 gametes

• ovum is source of 95% of trisomy cases

Diagnostic Testing

1. Amniocentesis or chorionic villus sampling (CVS)

2. NIPGD : Noninvasive prenatal genetic diagnosis

Amniocentesis or chorionic villus sampling (CVS)

fetal cells obtained from amniotic fluid or chorion of placenta

NIPGD : Noninvasive prenatal genetic diagnosis

fetal cells and DNA obtained from maternal circulation

Human Aneuploidy

1. Patau Syndrome (trisomy 13)

2. Edwards Syndrome (trisomy 18)

Patau Syndrome (trisomy 13) and Edwards Syndrome (trisomy 18)

• survive to term

• severe malformations

• early lethality

Patau Syndrome

• 47 , 13+

• infants not mentally alert

• deaf

• harelip

• cleft plate

• polydactyl

• general malformation of most organs

• life span < 6 months