Unit 3 – Matters of Sex & Multifactorial Traits

Chapter 6 – Pages 111- 129

Sex Chromosomes

  1. ______XY, ______XX
  2. Size Difference

X – medium size, ______

Y – ¼ size of X, ______

-63 ______genes that cancross-over with the X

X & Y are not ______

3. X-linked & Y-linked (______) genes

4. Females have 2 copies (alleles) of all X genes

Males have 1 copy

______– all genes on X expressed

Sex Ratio

Males – 50% X, 50% Y gametes

Expected 1:1 ratio in offspring

Observed ______males:______females at birth

Y sperm is ______, has more ______somore ______are conceived.

More males than females until age ______

Age 65 – _____ males:______females

Sex Differentiation

- depends on gene action within the embryo

- usually clear cut, but phenotype may differ from genotype

- 0-4 weeks the zygote is ______

- ______weeks the sexual development occurs

Making A Male (pg. 113)

  1. The presence of a Y chromosome (______gene) produces Testis Determining Factor (______) which causes the gonad tissue to develop into a ______.
  2. H-Y antigen is formed by a gene on the Y which blocks ______formation.
  3. Testes produce two hormones

A)Mullerian Inhibiting Hormone (MIH)

- causes the Mullerian (______) ducts to breakdown

B) Testosterone

- stimulates the ______(male) ducts to develop

- testosterone is converted in DHT which develops ______male

organs

Making A Female

  1. The absence of a Y chromosome causes the gonad tissue to develop into an______.
  2. If testes are not formed, there will be no:

A)______present so Wolffian ducts breakdown.

B)MIH present so Mullerian ducts develop forming the ______internal organs.

Testicular Feminization (Androgen Insensitivity) X-linked

- genotypic males develop as ______females

- genotype is XY so ______develop

- MIH breaks down Mullerian ducts internally, so ______develop inside.

- a gene mutation prevents tissue from responding to testosterone (______

______are lacking).

- tissues externally develop as ______since testosterone has no effect.

- detected due to no ______

- vagina is present, but no ______

- undescended testes result in a high incidence of cancer, so they are usually

______.

______(Intersexuals) – 1/83,000

- usually are XX with some Y material found on an ______.

- ovaries are usually on the ______, testes on the ______

- usually______

Pseudohermaphrodites – rare, XY genotype

- ______internal development

- testosterone not converted so external ______development occurs

- at puberty: ______so female becomes morelike a male (sterile)

- most common in the ______

Precocious Puberty - autosomal recessive

Boys – early as age ______

- well developed ______, small ______, enlarged______

- ______in height

Girls – at puberty ______

X-linked Dominant Traits – rare

- more serious in ______

- found more commonly in ______

Congenital Generalized Hypertrichosis

Hypophosphatemia

X-linked Recessive Traits

- fairly common because carriers are not ______

- much more common in ______

Colorblindness

Duchenne’s Muscular Dystrophy

Hemophilia (Needle Stick)

Ichthyosis

How do females get X-linked recessive traits?

  1. ______
  2. Turner’s Syndrome (______)
  3. ______with a mutation
  4. ______recessive genes

Y-linked Traits (______)

- ______to son transmission

- only affects ______

- few traits are known (maleness, ______, infertility)

Dosage Compensation

Even though females have 2 X chromosomes (to a male’s one), the products produced from her genes are ______to a male (not more!). How?

______

One of a female’s X chromosomes crumples up like a paper wad, and condenses into a dark staining mass in the nucleus. Why?

X-inactivation & Barr Bodies

Dosage is the same in females because one of the X chromosomes is ______.

- Each cell is unique, because either X chromosome can be inactivated

forming a ______.

-Once a cell decides which X to inactivate, all ______of

that cell carries the same inactivated X chromosome.

-Females may be mosaics for ______traits. Page 123

Sex-Influenced Genes – dominant in one sex, but recessive in the other

-influenced by ______

-for the opposite sex to show the same trait, they must be ______

Males – autosomal dominant

  1. ______– high testosterone levels
  2. ______– day 34-35 mistake
  3. ______– buildup of sodium urate crystals

Females – autosomal dominant

  1. ______
  2. ______– day 24-25 mistake (1/1000 ______)

- ______(green leafy vegetables, oranges, corn, beans etc.) can

reducedefects 50-70%

3. Index finger ______than fourth ______

Sex-limited Genes

-genes can be transmitted by either parent, but are ______

-Expressed only in one sex (______)

Hydatidiform Mole – “______pregnancy” – ______

-fertilized egg forms a ______

-the longer it stays, the greater the chance of it becoming ______

-all of mole must be ______

Study of mole – ______

-all chromosomes are from ______

-sperm enters an egg without a nucleus

- sperm DNA ______

- only survives with a ___ sperm, ______= miscarriage

Genomic Imprinting – identical genes behave differently depending upon the ______

of the contributing parent. Page 127

- when individuals produce sex cells, the ______are erased, and new

onesspecific to the sex of an individual are imposed on all gamete

chromosomes

- imprint = temporarily blocking certain genes with ______groups (CH3)

Chapter 7 – pages 132 – 138

Polygenic Traits – more than ______making a trait.

-continuously ______

Multifactorial Traits – those traits affected by the ______.

Polygenic & Multifactorial Examples – ______

______

Distribution Charts – page 137