Question

Human Genetics

Although we humans are fantastically made, are quite complex, and our traits are often coded by many genes, some traits are coded by single gene pairs. The following table is a survey to help you determine your genotype, based on phenotype traits. Keep in mind the terms homozygous dominant (AA) will have the dominant trait, homozygous recessive (aa) will have the recessive trait, and heterozygous (Aa) will have the dominant trait. If you have the dominant trait, you will likely not be able to determine if you are homozygous dominant or heterozygous, unless you know what traits your parents have, so you will circle “RR or Rr” if you are dominant for the first trait, for example, because you can’t know if you are RR or Rr for sure.

Fill in the chart provided and then survey a minimum of 6 people (unrelated if possible) and find out the total who are dominant and recessive for the trait.

A. Look at the phenotypic trait and description (use human traits document)
B. Decide if you express the trait and fill in the dominant or recessive box

Trait Description	Phenotype (please circle only one row)	Genotype (please circle only one row)	I am (Dominant or Recessive)	# of people Dominant	# of people Recessive
Tongue rolling (ability to roll tongue)	Roller Non-Roller	RR or Rr rr
Bent little fingers (last portion of the pinky bent inward towards other fingers)	Bent pinky Straight pinky	BB or Bb bb
Widow’s peak (peak in the forehead hairline)	Present Absent	WW or Ww ww

Hitchhiker’s Thumb (ability to hyper extend the thumb)	Present Absent	HH or Hh hh
Hand clasping, left over right thumb	Left on top Right on top	LL or Ll ll
Freckles	Present Absent	FF or Ff ff
Free earlobe (either attached to side of head or dangle free, see diagram)	Free Attached	HH or Hh hh
Chin cleft (dimple in middle of chin	Present Absent	CC or Cc cc
Hair on middle joints of fingers (Hairs present between the first and last finger joints)	Present Absent	HH or Hh hh
Short second finger (ring finger shorter than pointer finger—note, ring finger short in males is dominant, in females recessive)	Ring finger shorter Ring finger longer	SS or Ss ss
Dimples (dimples in one or both cheeks)	Dimples Present Dimples Absent	DD or Dd dd
Eye Color (blue?)	Other than blue blue	BB or Bb bb

Blue eyes: When a person is homozygous for a recessive gene no pigment is deposited in the from part of the eye and a blue layer at the back of the iris shows through. A dominant gene, allows pigment to be deposited which masks the blue color. Other genes are responsible for the type and amount of this pigment leading to various shades of brown, hazel, green and other colors.

Please help me fill out this chart. Thank you!

Answer 1

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