Unit 7: Mendelian Genetics Flashcards
1
Q
gene
A
- a segment of a DNA molecule that gives the instructions for making proteins
- passed from parent to offspring
- they separate each other when gamets are formed
2
Q
melanin
A
-the pigment which contributes to the color of skin and hair
3
Q
alleles
A
- different versions of genes
- alleles for different genes usually separate independently from one another
- if 2 or more forms/alleles of the gene for the same trait exist, some are dominant and others may be recessive
4
Q
Punnett Square
A
- the gene combos that might result from a genetic cross
- mom on the top
- dad of the side
5
Q
genetics
A
the study of geredity
6
Q
homozygous
A
- both copies of the same allele for the same trait (BB, bb)
- true breeding
7
Q
heterozygous
A
- type of gene combo of 2 different alleles for the same trait (Bb)
- aka: hybrid for particuar trait
8
Q
dominant allele
A
- capital letter
- observed trait
- normal, funcional enzyme
9
Q
recessive allele
A
- lower-case letter
- hidden trait
- non-funcional enzyme
10
Q
genotype
A
-genetic makeup of an individual (allele combination)
11
Q
phenotype
A
-observable physical and physiological characteristics of an individual
12
Q
probability
A
- the likelihood that a particular event will occur
- predict the average outcome of a large number of events
- cannot predict the precise outcome of an individual event
- in genetics, the larger the # of offspring, the closer the resulting # will get the expected values
13
Q
the principles of probability
A
-used to predict the outcomes of genetic crosses
14
Q
F1
A
-1st generation of offspring
15
Q
P
A
-parent generation
16
Q
F2
A
-2nd generation of offspring
17
Q
Gregor Mendel
A
- known as the father of genetics
- high school teacher, took care of the school’s garden (pea plants)
- became curious about how the plants passed on certain traits (color height…etc)
- established 3 principles…..
1. Principle of Dominance and Recessive: one trait is covered up by another trait
2. Principle of Segregation; the two alleles for a trait separate during meiosis
3. Principle of Independent Assortment: traits separate independently of one another during meiosis - performs a 2-factor cross to see if different traits would sepaarate
- exceptions= incomplete dominnce, codominance, multiple alleles , polygenetic traits
18
Q
heredity
A
-passing of characteristics from parent to offspring
19
Q
independent assortment
A
- genes that separate independently of one another during meiosis
- genes that segrgate independently do not influence each other’s inheritance
- 9:3:3:1 ratio in F2 generation
20
Q
incomplete dominace
A
- when 1 allele is not completely dominant over the other
- the heterozygous phenotype is between the 2 homozygous phenotype (AA = grey is between AA= black and aa= white)
21
Q
codominance
A
- both alleles contribute to the phenoptype
- both phenotypes contribute to the offspring’s phenotype (spots)
22
Q
multiple alleles
A
- genes that are controlled by more then 2 alleles
- ex: a rabbit’s coat color is determined by a songle gene that has at least 4 different alleles
23
Q
polygenetic traits
A
- traits controlled by 2 or more genes
- ex: skin color= controlled by 4 different genes; eye/hair color
24
Q
Type A
A
-IA IA; IA i
25
Type B
-IB IB; IB i
26
Type AB
IA IB
27
Type 0
i i
28
cross fertilization
-pollen from 1 flower fertilized egg from another flower
29
self fertilization
-pollen fertilizes egg from the same plant
30
pedigree
- shows patterns of inheritance
- uses family tree and info about affected individuals.....
1. to figure out th genetic basis of a disease or trait
2. to predict thhe risk of disease in fitire offspring in a family
- basic patterns of inheritance......
* autosomal, recessive
* autosomal, dominant
* sex-linked, recessive
* sex-linked, dominant (very rare)
31
sex-linked inheritance
- recessive
- sex linked traits are carried on the X chromosome
- nothing on the Y chromosome
- males exhibit sex-linked traits more because females will only exhibit sex linked trait if she recieves 2 allels for that 1 trait (1 one each X chromosome) and males only need 1 X chromosome, on which the trait is carried on
32
Y chromosome
-makes sure that half the human population is male and half is female
33
autosomal, recessive traits
- rare in predigree
- often skips a generation
- affects males and females equally
- hidden in heterozygous carriers
- diseases.....
1. Cystic Fibrosis (mucus clogs organs)
2. Sick Cells Anemia (irregular shaped blood cells; blood can't carry enough oxygen)
3. Phenylketonuria (PKU)= failure of brain to develop in infancy
4. Tay-Sachs disease (infants die at an early age)
- For each of these, overdominance (heterozygote superiority) has been suggested as a factor in maintaining the disease alleles at high frequency in some populations
34
autosomal, dominant traits
- Trait is common in the pedigree
- Trait is found in every generation
- Affected individuals transmit the trait to ~1/2 of their children (regardless of sex)
- few disease
- ex: achondroplasia (a sketelal disorder causing dwarfism)
35
sex-linked, recessive traits
- Trait is rare in pedigree
- Trait skips generations
- Affected fathers DO NOT pass to their sons
- males are more often affected than females
- ex: hemophilia
- ex: Glucose-6-Phosphate Dehydrogenase deficiency (hemolytic disorder causes jaundice in infants and (often fatal) sensitivity to fava beans in adults)
36
sex-linked, dominant traits
- Trait is common in pedigree
- Affected fathers pass to ALL of their daughters
- males and females are equally likely to be affected
- X-linked dominant diseases are extremely unusual (Often lethal (before birth) in males and only seen in females)
- ex: incontinentia pigmenti (skin lesions)
- ex: X-linked rickets (bone lesions)
37
Incomplete Penetrance of autosomal dominant traits
- not everyone with genotype expresses trait at all
| - ex. Breast cancer genes BRCA-1 and BRCA-2 & many “genetic tendencies” for human diseases
38
Sex-limited expression
-trait only found in males OR females
39
Pedigree Analysis in real life
- dominant traits may be rare in population
- recessive traits may be common in population
- alleles may come into the pedigree from 2 sources
- mutation happens
- often traits are more complex
- affected by environment & other genes
40
Aneuloidies
- abnormal number of chromosomes caused by nondisjunction
- ex: down syndrome= trisomy on chromosome 21; 3 copies of a chromosome
- ex: Turner Syndrome= inherit only X chromosome in females (XO)
- ex: Klinefelter Syndrome= extra X chromosome in males (XXY)-
