Chapter 6 Genetics

During 5th week of prenatal developed all embroyos will develop two sets of

-Unspecialized gonads

reproductive ducts: Mullerians(females) and Wolffians(Males)

SRY gene

Sex determining gene region of Y chromosome.

-Serves as transcriptor for the male phenotype.

Wnt4

-essential for the development and maturation for biological female.

-Contributes female phenotype but it’s not x chromosome it’s an autosome.

-males have this gene but it’s not expressed.

Heterogametic

different sex chromosomes.

-determines sex of the offspring.

-Human males have this XY

Homogametic

same sex chromosomes.

-Human females have this XX.

Psuedoautosomal Region

-Small region where X and Y are identical.

-Allows X and Y to pair with each other spermatogenesis.

X Chromosome

Contains more than >1500 genes.

-Much larger than Y chromosome.

-Acts a homlog to Y chromosome in males.

Y chromosome

Contains 231 genes

Does not cross over all it’s length

DNA segments acts as palidrome destablizes DNA replication.

2/3 of Y chromosome are heterochromatin: condensed version of chromatin does not contain any genes.

Anatomy of the Y chromosome

has a very short arm and a long arm

Psuedo Autosomal Regions (Par 1 and Par 2)

5% of the chromosome.

-Contains 63 genes shared with the X chromosome.

-Control bone growth, cell division, etc in both sexes

Male Specific Region (MSY)

-Makes of most of the chromosome.

-Three classes of DNA sequences:

sequences are identical to x chromosomes somewhat identical to x chromosome palindrome.

-Many genes are essential to fertility such SRY.

AZF

encodes a protein essential for producing sperm.

SRY (more detailed explanation)

-Encodes a transcriptor factor protein controls the expression of other genes including SOX9.

-stimulates male development.

-sends signals to indifferent gonads to destroy female structures.

Secretes Testrone and DHT (Dihydrotestrone) to stimulate the development of male reproductive structures.

Hermaphorditism

Is an older and more general term used to describe an individual with both male and female structures

Intersex

-May have exeternal genitalia of one sex but may have internal genitalia of the other sex or Gentalia is ambigious.

Psuedohermaphoditism

presence of both and female structures at different life stages.

Androgen Insentivity Sydrome

-Mutations on the x chromosome blocks formation of androgen receptors.

-Phenotypically appear female but don’t you don’t female reproductive organs you have testes but unable to reproduce testerone.

5 Alpha Reductase Deficiency

Unable to convert Testerone (Internal Development) to DHT (Exeternal Development)

-Child inside has male anatomy but looks like a girl on the exterior.

Congential Adrenal Hyperplasia

-Enzymes blocks causes androgens to accumulate.

-Causes Precocious puberty in males and secondary male characterisitics in females.

Chromsomal/Genetic Sex

XY= males

XX- females

Gondal sex

undifferentiated structures turn into testes or ovaries

Phenotypical Sex

development of internal and exeternal reproductive structures continues as male or female in response to hormones.

Gender Indentity

strong feeling of being male, female, or non binary develop

Sexual Orenitation

Attraction to the same gender or opposite gender

Sex Ratios

-Proportion of male to females in a human population.

Primary Sex Ratio

at conception

Secondary Sex Ratio

at birth

Teritary Sex Ratio

at maturity.

Y linked

genes coded on the Y chromosome.

-rare

-transmitted to male to male.

-Do not have dominant or recessive traits they only one copy of each gene.

Hemizygous

only have one copy of the gene.

-Males are hemizygous because they only one copy X and Y chromosome.

Holandric Inheritance

Y linked inheritance passed down to all offspring.

X linked traits

Females- X linked traits passed it down like autosomal traits.

Males: A single copy of an X linked allele causes expression of the trait or illness.

Males are considered hemizygous for the x linked traits.

X linked recessive

-Females you have to be homozygous recessive to express it.

-If the man has it they will express it.

-It will be passed down to their daughters making them carriers.

Xlinked Dominant

-Females need one copy to express it:
Heterozygous: 50% of expressing it.

Homozygous: 100% chance of expressing it.

-Males who inherit it are more severely affected because they have no other allele to mask it’s affect.

Males will express it and they will pass to all their daughters will express it but none their sons.

-Most cases are result of new mutations rather transmissions from parents.

Sex limited traits

Traits often present in a single sex.

-Genes may be auotosomal or x linked.

Precious Puberty

you undergo puberty at a younger age than average. Autosomal Dominant only present in males females never express it.

Sex influenced traits

-Presence in both sexes but dominant in one sex and recessive in the other.

-Can be autosomal or x linked.

-Differences in expression can be caused by hormonal differences in between both sexes.

XIST gene

on the x chromosome expresses for RNA molecule that coats a chromosome that makes x chromosome tightly packed and inactive.

Barr Body

X chromosome that’s compacted and inactive

X inactivation

-Happens in female mammals.

-One x chromosome stays active and the other x chromosome stays condensed.

-Balances inequality expression in x chromosomes.

-Females are mosiac for the most expression of genes in the x chromosome.

Epigentic Change

Inherited change that does not alter the DNA sequence

-Inactive DNA has methyl groups that prevent it from being transcribed into RNA.

Effects of inactivation of the phenotype

-X inactivation can be used check the sex person.

-Nucleus of the female during interphase contains a barr body.

The consequences of x inactivation:

Homozygous x linked traits: no effects

Heterzygous: expression one of allele or another.

Manifesting Heterzygote

A female expressing the phenotype corresponding to an x linked gene.

Genomic Imprinting

-Gene expression depends whether inherited from the mother or father one alllele is expressed awhile the other one is silenced.

Methyl groups bind genes or several linked genes preventing them from being expressed.

-For an imprinted gene the copy inherinted from mom or dad is always covered up with methyl groups.

Parental effect

on gene expression is seen as diseases inherited by from a parent.

Epigentic Alteration

layer of meaning stamped upon a gene without changing it’s DNA sequence

Genomic Imprinting 2

-Imprints are erased during meiosis.

-Reassigned based on the according sex of an individual.

Imprinted genes are in clusters along the chromosome controlled by imprinting centers

-one gene in the cluster could be esstestinal for early development.

-other cans be imprinted due to bystander effect.

Researchers suggest that it takes two opposite sex parents to produce a healthy embryo

Male genome controls placenta development.

Female genome controls embroyo development.

Uniparental disomy

both 15s came from the same parent

Deletion of 15 chromosome

reveals imprinting.

Transcription Factor

protein activates transcripiton of other genes.

-SRY activates it

Organ Reproduction

SRY turns gonads into testes one of hormones that produces testerone and DHT.

-With SRY malarine ducts will degrade and wolfene ducts which are going to turn to vas deferens and different glands.

-Without SRY genes those develop into ovaries. Wolferine ducts will degrade and malarine ducts differiente to uterus, uterine tube, and vagina.

X inactivation 2

-Occurs early in prenatal development.

-Adult females will have patches of tissue that differ in expression of their x linked genes.

-Alters phenotype not the genotype.

-An example of this epigenetic change:
-an inherinted change that does not always alter DNA sequences. .

-Inactive DNA has methyl groups bind it preventing from being transcribed