Science 6B Flashcards
What are Mendel’s factors called today?
Alleles
How many chromosomes does a normal human cell have?
46 chromosomes (23 pairs)
What do the letters along the top and side of a Punnett square represent?
Mother on top
Father on side
(dimples is dominant over no dimples)
A woman who is purebred for dimples marries a man who is hybrid for dimples. Is it possible for any of their children not to have dimples? Draw a Punnett square to prove your answer.
No, D dominates d in all four boxes
Explain the difference between incomplete dominance and codominance.
Incomplete dominance: Traits blend together. NO trait is overly dominate over the other. they blend traits (red and white = pink)
Co- dominance: NO blending. Both traits are equally dominate, so both appear. Brown and white parent cows have a brown and white calf. Both traits are shown
The condition where two or more genes work together to produce a certain trait is called
a. a sex-linked trait
b. multiple alleles.
c. incomplete dominance.
d. polygenic inheritance
Polygenic inheritance
Genes must work together
How would you represent the genotype for a woman who is hybrid for type A blood?
a. XAi
b. IAi
c. IAIA
d. XAYi
B. IAi
good example of multiple alleles for a single trait in hu- mans is blood types.
IAIA is purebred for A blood
IAi is hubrid for A blood
(i is type O and is recessive)
A woman with type O blood marries a man with type AB blood. Is it possible for any of their children to have type O blood? Explain.
No. In order to have type O blood, a person must be purebred recessive (ii); he cannot have either dominant allele.
Write the genotypes for a female carrier of red-green colorblindness and a normal male.
?
________ ________ is a model used to represent genetic crosses.
Punnett squares
This is a grid that is divided into four boxes and uses letters to represent alleles.
Punnett square
If TT and tt were used as parents on a Punnett square, all the inside boxes would have the same genotype… What would it be?
What would the phenotype be?
(T, t)
Tall plants
This is when two different alleles for the same trait are both expressed, resulting in a blending of the two forms of that trait.
(red and white flowers make pink)
Incomplete dominance
A Punnett square can have 4 or more boxes, but What does the number of boxes mean?
Generic possibilities of their offspring
True or False: The number of boxes in a Punnett square is equal to the number of offspring the parents had?
False. Its the number of genetic possibilities
Make Punnett Squares to find the following:
How many different genotypes of a TT × tt purebred cross?
How many different genotypes for a Tt × Tt hybrid cross?
One (T, t)
Three (T, T), (T, t), (t, t)
This Is when there is no pure dominant or pure recessive allele expressed (phenotype)
Incomplete dominance
What are the three variations to Mendel’s theories?
Incomplete dominance: red + white = pink
Codominance: Brown + white = brown and white
Polygenic inheritance: multiple genes result in unique trait
Give some examples of polygenic inheritance where two or more genes “work together” to make one trait:
Skin color Hair color height intelligence body type
________ _________ are the chromosomes that determine whether an organism is male or female.
Sex chromosomes
A normal human has 23 pairs of chromosomes. which one determines the persons sex (gender)?
23
What two alleles do female and male sex chromosomes have? same or different?
(Remember, most traits dont matter if the organism is a bot of girl, except for these traits on the sex chromosomes)
XX
XY
What determines if a kid will be a boy or girl? The mom’s chromosomes or the fathers chromosomes?
the X or Y chromosome of the father’s sperm determines the sex of the child (50-50’chance)
Some inherited traits are controlled by genes located on the sex chromosomes (X or Y). These traits are called ________ ________.
Sex-linked traits
The Y chromosome is smaller than the X and has a few genes. Therefore, most sex-linked traits are on which chromosome, X or Y?
X chromosome
If on the X, its not on the smaller Y
Its hard to tell the difference between boy and girl chicks. Reginald Punnett discovered that the color of certain feathers is a sex-linked trait.
True. Helped war country only save female chicks to make eggs
__________ are people who have the allele for a trait but do not exhibit the trait them- selves.
Carriers
Create a Prunnett Square to find out why Juliet has blue eyes:
What are the odds of our next kid having blue eyes (phenotype)?
50-50
