chapter 8 notes (day 5)
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Chapter 8 Notes (Day 5). Objective: 1) Provide an example for codominance, incomplete dominance, and multiple alleles. 2) Define karyotype. SIMPLE DOMINANT HEREDITY. SOME TRAITS THAT ARE DOMINANT INCLUDE: HITCHHIKER’S THUMB, ALMOND-SHAPED EYES, THICK LIPS, HAIR ON MIDDLE SECTION OF FINGER. - PowerPoint PPT PresentationTRANSCRIPT
Objective: 1) Provide an example for codominance, incomplete dominance, and multiple alleles. 2) Define karyotype.
SOME TRAITS THAT ARE DOMINANT INCLUDE:
HITCHHIKER’S THUMB, ALMOND-SHAPED EYES, THICK LIPS, HAIR ON MIDDLE SECTION OF FINGER.
.
Human Traits: autosomal1. Shape of face (probably polygenic)
Oval dominant, square recessive
2. Cleft in chin No cleft dominant, cleft recessive
3. Hair curl (probably polygenic) Assume incomplete dominance
Curly: homozygousWavy: heterozygousStraight: homozygous
4. Hairline Widow peak dominant, straight hairline recessive
5. Eyebrow size Broad dominant, slender recessive
6. Eyebrow shape Separated dominant, joined recessive
7. Eyelash length Long dominant, short recessive
8. Dimples Dimples dominant, no dimples recessive
9. Earlobes Free lobe dominant, attached recessive
10. Eye shape Almond dominant, round recessive
11. Freckles Freckles dominant, no freckles recessive
12. Tongue rolling Roller dominant, nonroller recessive
13. Tongue folding Inability dominant, ability recessive
14. Finger mid-digital hair Hair dominant, no hair recessive
15. Hitch-hiker's thumb Straight thumb dominant, hitch-hiker thumbrecessive
16. Bent little finger Bent dominant, straight recessive
17. Interlaced fingers Left thumb over right dominant, right over left recessive
18. Hair on back of hand Hair dominant, no hair recessive
19. Tendons of Palmar Muscle Two tendons dominant, three tendons recessive
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INCOMPLETE DOMINANCE: THE PHENOTYPE OF THE HETEROZYGOUS CONDITION IS A CROSS BETWEEN THE DOMINANT AND RECESSIVE TRAITS.
EXAMPLE: IN CARNATIONS, R=REDr=WHITE
RR= RED CARNATION
Rr= PINK CARNATION
rr= WHITE CARNATION
CODOMINANCE: THE PHENOTYPES OF BOTH ALLELES ARE EXPRESSED IN A HETEROZYGOUS INDIVIDUAL.
EXAMPLE:
IN CHICKENS, B= BLACK FEATHERS, W= WHITE FEATHERS
BB = BLACK FEATHERS
BW = BLACK AND WHITE FEATHERS
WW = WHITE FEATHERS
MULTIPLE ALLELES: SOMETIMES MORE THAN 2 ALLELES CONTROL A TRAIT.
3 ALLELES DETERMINE PIGEON FEATHER COLOR
Occurs when one gene controls the expression of a second gene.
In mice, one gene controls whether the mouse will have coloration (dominant) or albinism/white (recessive). IF coloration is dominant, THEN a second gene will determine if the mouse will be brown or black.
Pleiotropy is a condition that occurs when 1 gene controls many phenotypes.
A classic example of pleiotropy is the human disease PKU (phenylketonuria). This disease can cause mental retardation and reduced hair and skin pigmentation, and can be caused by a mutation in a single gene that codes for an enzyme (phenylalanine hydroxylase) that converts the amino acid phenylalanine to tyrosine, another amino acid.
One trait or phenotype is controlled by many genes.
For example between 4 to 10 genes control human height.
Genes linked to human height: ZBTB38, HHIP, CDK6, HMGA2, GPR126, ADAMTSL3, GDF5, LCORL, EFEMP1, and HIST1H1D
AUTOSOMES: THERE ARE 22 PAIRS OF HOMOLOGOUS CHROMOSOMES (TOTAL CHROMOSOMES =44)
SEX CHROMOSOMES: 1 PAIR OF CHROMSOMES THAT DETERMINE THE SEX OF AN ORGNANISM. SOME TRAITS ARE CONTROLLED BY GENES LOCATED ONLY ON THE SEX CHROMOSOMES (EXAMPLE: COLOR BLINDNES AND HEMOPHILIA).
YOUR CHROMOSOMES DURING METAPHASE
YOUR CHROMOSOMES ORGANIZED AS A KARYOTYPE (CHROMOSOME MAP)
SEX-LINKED TRAITS: TRAITS CONTROLLED BY GENES LOCATED ON THR SEX CHROMOSOMES.
X = FEMALE SEX CHROMOSOME
Y = MALE SEX CHROMOSOME (SMALLER THAN X AND DOES NOT CONTAIN AS MANY GENES)
THOMAS HUNT MORGAN DISCOVERED TRAITS LINKED TO SEX CHROMOSOMES. HE FIRST NOTICED THIS IN FRUIT FLY EYE COLOR.
MORGAN’S 1ST EXPERIMENT:
FEMALE MALE
X
Xr Y
XR
XR
XRXr XRY
XRXr XRY
OFFSPRING: ALL RED EYES