Unit 7: Mendelian Genetics Flashcards Preview

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Flashcards in Unit 7: Mendelian Genetics Deck (40)
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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
Q

Type B

A

-IB IB; IB i

26
Q

Type AB

A

IA IB

27
Q

Type 0

A

i i

28
Q

cross fertilization

A

-pollen from 1 flower fertilized egg from another flower

29
Q

self fertilization

A

-pollen fertilizes egg from the same plant

30
Q

pedigree

A
  • 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
Q

sex-linked inheritance

A
  • 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
Q

Y chromosome

A

-makes sure that half the human population is male and half is female

33
Q

autosomal, recessive traits

A
  • 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
Q

autosomal, dominant traits

A
  • 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
Q

sex-linked, recessive traits

A
  • 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
Q

sex-linked, dominant traits

A
  • 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
Q

Incomplete Penetrance of autosomal dominant traits

A
  • not everyone with genotype expresses trait at all

- ex. Breast cancer genes BRCA-1 and BRCA-2 & many “genetic tendencies” for human diseases

38
Q

Sex-limited expression

A

-trait only found in males OR females

39
Q

Pedigree Analysis in real life

A
  • 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
Q

Aneuloidies

A
  • 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)-