Unit 7: Mendelian Genetics

Question 1

gene

Answer 1

• 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

Question 2

melanin

Answer 2

-the pigment which contributes to the color of skin and hair

Question 3

alleles

Answer 3

• 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

Question 4

Punnett Square

Answer 4

• the gene combos that might result from a genetic cross
• mom on the top
• dad of the side

Question 5

genetics

Answer 5

the study of geredity

Question 6

homozygous

Answer 6

• both copies of the same allele for the same trait (BB, bb)

- true breeding

Question 7

heterozygous

Answer 7

• type of gene combo of 2 different alleles for the same trait (Bb)
• aka: hybrid for particuar trait

Question 8

dominant allele

Answer 8

• capital letter
• observed trait
• normal, funcional enzyme

Question 9

recessive allele

Answer 9

• lower-case letter
• hidden trait
• non-funcional enzyme

Question 10

genotype

Answer 10

-genetic makeup of an individual (allele combination)

Question 11

phenotype

Answer 11

-observable physical and physiological characteristics of an individual

Question 12

probability

Answer 12

• 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

Question 13

the principles of probability

Answer 13

-used to predict the outcomes of genetic crosses

Question 14

F1

Answer 14

-1st generation of offspring

Question 15

P

Answer 15

-parent generation

Question 16

F2

Answer 16

-2nd generation of offspring

Question 17

Gregor Mendel

Answer 17

• 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

Question 18

heredity

Answer 18

-passing of characteristics from parent to offspring

Question 19

independent assortment

Answer 19

• 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

Question 20

incomplete dominace

Answer 20

• 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)

Question 21

codominance

Answer 21

• both alleles contribute to the phenoptype

- both phenotypes contribute to the offspring’s phenotype (spots)

Question 22

multiple alleles

Answer 22

• 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

Question 23

polygenetic traits

Answer 23

• traits controlled by 2 or more genes

- ex: skin color= controlled by 4 different genes; eye/hair color

Question 24

Type A

Answer 24

-IA IA; IA i

Question 25

Type B

Answer 25

-IB IB; IB i

Question 26

Type AB

Answer 26

IA IB

Question 27

Type 0

Answer 27

i i

Question 28

cross fertilization

Answer 28

-pollen from 1 flower fertilized egg from another flower

Question 29

self fertilization

Answer 29

-pollen fertilizes egg from the same plant

Question 30

pedigree

Answer 30

• 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)

Question 31

sex-linked inheritance

Answer 31

• 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

Question 32

Y chromosome

Answer 32

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

Question 33

autosomal, recessive traits

Answer 33

• 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

Question 34

autosomal, dominant traits

Answer 34

• 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)

Question 35

sex-linked, recessive traits

Answer 35

• 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)

Question 36

sex-linked, dominant traits

Answer 36

• 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)

Question 37

Incomplete Penetrance of autosomal dominant traits

Answer 37

• not everyone with genotype expresses trait at all

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

Question 38

Sex-limited expression

Answer 38

-trait only found in males OR females

Question 39

Pedigree Analysis in real life

Answer 39

• 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

Question 40

Aneuloidies

Answer 40

• 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)-