Lecture 11 Flashcards
So far we learned about the 2 laws from Mendel, name them
The Law of Segregation and The Law of Independent Assortment
Which Law is connected to monohybrid and dihybrid crosses?
Segregation = Mono (dom/rec alleles)
Ind. Assortment = Di (2 separate genes)
Name all 10 aspects BEYOND Mendel
a) Incomplete Dominance
b) Codominance
c) Multiple Alleles
d) Epistasis
e) Pleiotropy
f) Polygenic Inheritance
g) Sex-linked Inheritance
h) Variation in Chromosome Number
i) Variations in Chromosome Structure
j) Genes and the Environment
What is an Incomplete Dominance?
it’s a blending of traits
(neither allele is dominant); instead, they blend together
So what does Incomplete Dominance mean (think of the genotype)?
The heterozygous form is intermediate b/w that of the 2 homozygous forms
Let’s use an example to solidify our comprehension: what happens if you crossbreed a red flower and a white flower…
In an incomplete dominance, you might get a pink flower.
The pink flower is neither fully red nor fully white. It’s somewhere in between, showing a blend of both traits.
What is Codominance?
when both traits are equally expressed
So what does Codominance mean (think of the genotype)?
heterozygous simultaneously expresses the phenotype of both homozygotes
For example, let’s talk about cattle and horses. Imagine there are two coat colors: red and white. What would the result be in terms of co-dominance?
In codominance, neither color is dominant over the other.
= The offspring could be a mix of both colors. This mix shows up as patches of red and white all over the body.
What are these types of horses called?
roan
What involves 3 alleles?
ABO
However, why can an individual only have 2 regardless of how many alleles exist?
because you only have 2 pairs of homologous chromosomes for each of your 23 chromosomes
What are the 3 alleles for ABO?
I^A (type A), I^B (type B), i (type O)
What would be the alleles of a father AB and a hetero A Mother?
Father: I^A I^B
Mother: I^A i
Make a Punnett square out of this information, what are the possible offspring with the phenotypes and genotypes
check p. 7 for answers
Type A
Type AB
Type A
Type B
+ Do Baby Mix Up problem (p.8-9)
What is called the interaction between genes that influences a phenotype?
Epistasis
Define more epistasis:
The presence of certain alleles of one locus can PREVENT OR MASK the expression of alleles of a different locus
Definition of Pleiotropy: A single gene may affect ______ ________?
multiple phenotypes
When does Pleiotropy occur?
when different cell types use a gene product or have a signaling function on various targets
What are 2 main/common examples?
cystic fibrosis & sickle cell anemia
What is cystic fibrosis?
defective protein found in the plasma membrane of lungs, intestines, pancreas, liver, sweat glands
What is sickle cell anemia?
defective protein in red blood cells
leads to multiple symptoms (heart failure, jaundice, pain, etc.)
What is the term associated with this definition? Many
genes interact to affect the
expression of one trait
Polygenic Inheritance
What is Polygenic Inheritance? in basic words?
The inverse of pleiotropy
SO: traits influenced by several genes
What is a sex-linked Inheritance?
Deals with characteristics other than sex-related ones inherited on sex chromosomes (mainly X)
How many autosomes do we have?
22 pairs autosomes
How many sex chromosomes do we have?
1 pair of SEX CHROMOSOMES
How many kinds of sex chromosomes can we have?
2 kinds: X and Y
X: female
Y: male
How does the determination of sex happen?
Mom provides an X chromosome; the father can provide an X or Y
What are the different combinations and mention if it’s a girl or boy
XX girl
XY boy
Sex chromosomes contain genes that (give 3 points):
- determine the sex of individual (girl or boy)
- control the development of secondary sexual characteristics (breasts, deep voice…)
- can also carry genes for other characteristics (color blindness, hemophilia…)
TRUE or FALSE: Sex chromosomes are truly homologous
FALSE: they are NOT truly homologous
TRUE or FALSE:
they behave like homologues
YES, BEHAVE (small region where they are homologous)
Do they pair up during meiosis?
YES
TRUE or FALSE: Characteristics other than gender-related ones are not inherited on sex chromosomes
FALSE: they ARE inherited on sex chromosomes
(hemophilia…)
Say one fact about sex-linked characteristics
genes located on 1 of the sex
chromosomes (X or Y) but not the other
Name 2 x-linked genes diseases/problems:
- hemophilia
- Red-Green Colorblindness
What is dosage compensation?
mechanism that makes the 2 doses in the female and the single dose in the male equivalent
When you think of Dosage compensation, what do you directly associate it with?
Barr body
What is barr body?
dense, metabolically inactive X chromosome (To avoid over-expression of ‘X’ genes in females)
Tell me 3 important things related with X inactivation
1) Inactivation is random during early embryo
2) Mitotic daughter cells have same inactive X
3) All cells still have same genetic makeup °
What do you call the presence of multiple sets of chromosomes?
Polyploidy
What is Aneuploidy?
abnormalities caused by the presence of a single extra chromosome or the absence of a chromosome
What do both Polyploidy and Aneuploidy have in common?
both related to Abnormal chromosome number
What results in Aneuploidies?
nondisjunction
(abnormal # of chromosomes because of an abnormal meiotic division)
So what is nondisjunction?
when chromosomes fail to separate
TRUE OR FALSE: this only happens in sex chromosomes
FALSE: Can occur in autosomes AND in sex chromosomes
Name the particularity with
Disomy, Trisomy and Monosomy
Disomy: normal (2 of a kind)
Trisomy: extra chromosome (3 of a kind)
Monosomy: lack of one ch. (1 of a kind)
How is Down Syndrome related?
Down Syndrome = Trisomy 21 = autosomal aneuploidy
How many chromosomes?
47 chromosomes (extra chromosome #21)
What are some of the symptoms?
*facial features, short, heart defects
* mentally handicapped
* most are sexually underdeveloped or sterile
What is this: = XXX (♀)
Triple X syndrome
What is this: XXY (♂)
Klinefelter syndrome
they are male bc of Y ch + may have breast & other female characteristics
What is this: X0 (♀)
Turner syndrome
no Y ch so they are female
usually lack normal ovaries (small/underdeveloped)
What is this: 0Y (♂)
Death b/c you need an X to live
Main thing about nature vs nuture
The genes set the limits, the environment molds the phenotype within genes’ limits
So what is the equation of phenotypes?
Phenotypes = genotype + environment
How are genes (height) modified variety of environmental conditions?
diet & general health (lack of proper nutrients will stunt growth)
