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BI157 > Chapter 14 > Flashcards

Chapter 14 Flashcards

1
Q

What is character, and an example?

A

heritable feature that varies among individuals

example- flower color

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2
Q

What is a trait?

A

variant for a character

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3
Q

What is Mendel’s Pea Experiment? (6)

A

Ensured cross-pollination by removing the stamen of a pea plant and brushing pollen from another plant

Prevented self-pollination

Results in a zygote that develops into a plant embryo in a seed

Only tracked characters in two distinct, alternative forms (flower color)

Only did true breeding

Cross pollinated two contrasting varieties

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4
Q

What is true breeding? (2)

A

When parents always produce the same variety in the offspring

example- purple pea flowers always producing purple flowers

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5
Q

What is hybridization? (4)

A

Breeding two contrasting varieties

P generation- true-breeding parents

F1 generation- first filial generation

breeding of F1 generation plants produces F2 generation plants

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6
Q

What is the law of segregation? (5)

A

During Mendel’s experiment, the F1 generation was purple

F2 generation had a ratio of purple to white 3:1

Purple flowers were dominant

White flowers were recessive

This means white flower traits were hidden in the presence of the purple flower trait

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7
Q

What are Mendel’s Model concepts? (4)

A

Alternative versions of genes account for variations in inherited characters

For each character, an organism inherits two alleles of a gene, one from each parent

If two alleles at a locus differ, one is dominant (determines appearance) one is recessive

Law of segregation- two alleles for a heritable character segregate during gamete formation and end up in different gametes

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8
Q

What are alleles?

A

Alternative versions of genes

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9
Q

What is a Punnett square?

A

diagrammatic device predicting allele composition of offspring from a cross between individuals of known genetic makeup

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10
Q

What is a homozygous organism? (2)

A

organism with a pair of identical alleles for a character

Results from true breeding

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11
Q

What is a heterozygous organism?

A

organisms with two different alleles for a gene

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12
Q

What is a phenotype?

A

organism’s appearance or observable trait

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13
Q

What is a genotype?

A

organism’s genetic makeup

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14
Q

What is a testcross? (4)

A

Determines whether an organism is homozygous or heterozygous

Crosses said organism with a recessive homozygous allele

If all offsprings result with dominant traits, the mystery organism is homozygous

If offsprings result with various traits, the mystery organism is heterozygous

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15
Q

What are monohybrids? (2)

A

organisms that are heterozygous for one particular character being followed

F1 generation in Mendel’s experiment

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16
Q

What is a monohybrid cross? (2)

A

cross between monohybrid heterozygotes

Results in a 3:1 ratio between dominant: recessive

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17
Q

What is a dihybrid? (3)

A

individuals that are heterozygous for the two characters being followed in the cross

YyRr

Results in a 9:3:3:1 YR:Yr:yR:yr

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18
Q

What is the law of independent assortment? (4)

A

two or more genes assort independently

Each pair of alleles segregates independently of
each other pair of alleles during gamete formation

Applies only to genes located on different chromosomes

Nonhomologous

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19
Q

How do alleles segregate, and an example?

A

Independently of another gene’s alleles

example- a coin toss always has a ½ probability of being tails no matter the previous coin toss’ result

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20
Q

What is the multiplication rule for a monohybrid cross? (5)

A

Used to determine the probability of two or more independent events will occur together in some specific combination

Example- chance of two coins tossed at the same time with both resulting in tails

We multiply the probability of one event by the probability of the other event

Example: ½ (chance of one coin being tails) * ½ (probability of other coin being tails)= ¼

Example: when gametes fuse to form a zygote: ½ (probability of a sperm to have recessive trati) * ½ (probability of an egg to have a recessive trait)= ¼

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21
Q

What is the addition rule for a monohybrid cross? (4)

A

The probability that any one of two or more mutually exclusive events will occur

Used to determine the probability that an F2 organism from a monohybrid cross will be heterozygous

For example: dominant allele can come from the egg and the recessive allele can come from the sperm or vice versa

Gametes can combine to form heterozygous offspring in two mutually exclusive ways

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22
Q

How do you calculate a genetic problem?

A

example-
In monohybrid cross, Yy has
¼ chance being YY, ½ chance of being Yy, and ¼ chance being yy
In monohybrid cross Rr
¼ chance being RR, ½ chance being Rr, and ¼ chance being rr
To determine the dihybrid probability of YYRR
¼ (YY) * ¼ (RR)= 1/16
To determine the dihybrid probability of YyRR
½ (Yy) * ¼ (RR)= ⅛

23
Q

How to calculate three or more character crosses

A

Ex: PpYyRr * Ppyyrr
First, list all genotypes that fulfill asked condition
ppyyRR, PpYyRr, ppYyRr, etc.
Calculate the probability by multiplying individual allele pairs
ppyyRr= ¼ * ½ * ½
When a heterozygous and homozygous allele pairs cross, the probability of heterozygous offspring is ½
Add together the chances of the asked condition

24
Q

How can an inheritance of a gene deviate from Mendelian patterns? (3)

A

Inheritance of characters determined by a single gene can deviate from Mendelian patterns when alleles are not completely dominant or recessive

When genes have more than two alleles

When a single gene produces multiple phenotypes

25
Q

What is complete dominance? (3)

A

phenotype of the heterozygote and the dominant homozygote are indistinguishable

When the dominant allele overpowers the recessive allele

Example- Mendel’s peas, with purple flowers showing complete dominance

26
Q

What is incomplete dominance? (2)

A

-when hybrids have a phenotype somewhere between those of two parental varieties

Example- when a red and white snapdragon crosses to produce pink snapdragons
Results when heterozygote offspring has less red pigment than the homozygous parent

27
Q

What is codominance?

A

wo alleles each affect the phenotype in separate, distinguishable ways

28
Q

What is an example of codominance? (4)

A

MN blood groups

Homozygous M allele have red blood cells with only M molecules

Homozygous N alleles have red blood cells with only N molecules

Heterozygous MN groups have both M and N alleles and result with distinguishable effects from both groups

29
Q

How do dominance and phenotype interact? (2)

A

When dominant alleles and recessive alleles coexist in a heterozygote, they do not interact

During the path from genotype to phenotype, dominance, and recessiveness comes into play

30
Q

What is an example of dominance and phenotype? (5)

A

Mendel’s round (dominant) vs wrinkled (recessive) pea seed shape

The dominant allele has the code for an enzyme that converts unbranched forms of starch to branched from in the seed

Recessive allele codes for a defective form of the said enzyme, leading to an accumulation of unbranched starch

Excessive water enters the seed through osmosis. As the seed dries, it wrinkles

Dominant allele present prevents excess water from entering the seed and prevents wrinkling when drying

31
Q

How do allele and phenotype correlate?

A

For any character, the observed dominant/ recessive relationship of alleles depends on the level at which we examine the phenotype

32
Q

How does Tay-Sachs disease differ in dominant/recessive relationship? (7)

A

Tay Sachs disease (cannot metabolize certain lipids because of defective enzymes, causing excess lipids)

Results when a child inherits two copies of the Tay Sachs allele (homozygotes)

Organismal level- recessive

Biochemical level- incomplete dominance
Heterozygote lipid metabolization is between homozygous of normal alleles and homozygous of tay-sachs disease

Heterozygotes have enough lipid metabolization to prevent disease

Molecular level- codominant

Heterozygous individuals produce equal numbers of normal and defective enzymes

33
Q

What is the frequency of dominant alleles? (3)

A

Dominant alleles are not always more common

Example polydactyly (extra finger/ toe)

For those with polydactyly, the presence of a dominant allele results with said disorder

34
Q

How do multiple alleles interact? (6)

A

Although Mendel’s pea character’s genes had only two alleles, most genes have more

Example- ABO blood groups

Determined by three alleles: IA (type A), IB (type B), i (none)

Results with one of four types, A, B, AB, or O

A and B are carbohydrates found on the surface of red blood cells

O have neither

35
Q

What is pleiotropy?

A

Genes having multiple phenotypic effects

Associated with multiple symptoms of certain hereditary diseases like cystic fibrosis and sickle-cell disease

In garden peas, gene determining flower color also affects the color of the seed coat

36
Q

What is epistasis?

A

Phenotypic expression of a gene at one locus alters that of a gene at a second locus

37
Q

What is an example of epistasis? (5)

A

labrador retrievers

Black coat is dominant to brown coat (Bb)

Genotype must be bb for a brown coat

Second gene determines whether pigment will be deposited in the hair (Ee)

If second gene is homozygous recessive (ee), coat is yellow, no matter the genotype of black/ brown locus

38
Q

What is polygenic inheritance? (2)

A

Mendel studied characters as either or
Either purple or white flowers

Many characters are not discrete
Skin color or height

39
Q

What are quantitative characters? (3)

A

characters that vary in the population in gradations along a continuum

Indicates polygenic inheritance

Additive effect of two or more genes on a single phenotypic character

40
Q

What is an example of quantitive colors? (4)

A

Skin pigmentation- consists of three units of alleles- A, B, or C

AABBCC is very dark

aabbcc is very light

AaBbCc is median
Same shade as aaBBCc

41
Q

How do nature and nurture affect phenotype? (5)

A

The environment can affect phenotype

Example- tree having various leaf size, shape, greenness, depending on exposure to wind and sun

Example- humans having various height (nutrition), build (exercise), and skin shade (sun tanning)

Genotype is not associated with a rigidly defined phenotype

Blood count is affected by factors like altitude, physical activity, and infectious agents

42
Q

What does multifactorial mean?

A

many factors influencing phenotype

43
Q

What is pedigree? (2)

A

a family’s history for a particular trait

Collecting information on said trait by looking through the family tree

44
Q

What are carriers? (2)

A

carry recessive alleles responsible for a disorder

Heterozygotes that do not exhibit the disorder but carry the recessive allele

45
Q

How does inbreeding affect inheritance?

A

Inbreeding raises chances of passing recessive alleles because they share common ancestors that are more likely to carry the same recessive allele

46
Q

What is cystic fibrosis? (5)

A

Most common lethal genetic disease in the US

More common in European descendants

Defective chloride transport chains in the plasma membrane

Results in a high concentration of chloride in the extracellular matrix

Causes mucus buildup in the organs

47
Q

How do recessive genes and sickle cell disease interact? (4)

A

Two recessive sickle cell alleles are necessary for full-blown disease
The presence of one allele can affect phenotype

Organismal level- incomplete dominant

Molecular level- codominant

48
Q

What are examples of dominantly inherited disorders? (4)

A

Achondroplasia- dwarfism

99.9% of the population are homozygous for the recessive allele

Huntington’s disease- a degenerative disease of the nervous system

A dominant lethal allele that shows no phenotypic effect until 35-45 years

49
Q

What are multifactorial disorders? (2)

A

Genetic component plus the significant environmental influence

Example-heart disease, diabetes, cancer, alcoholism, schizophrenia, bipolar disorder

50
Q

What is amniocentesis? (3)

A

technique to determine whether a fetus has tay sachs disease

Done in the 14th -16th week

Doctor inserts a needle in the uterus and extracts amniotic fluid

51
Q

What is chorionic villus sampling?

A

doctor inserts a narrow tube through the cervix into the uterus and suctions a sample of tissue from the placenta

52
Q

What are imaging techniques? (3)

A

examines fetus for major anatomical abnormalities

Ultrasound- sound waves used to produce an image

Fetoscopy- needle-thin tube containing a viewing scope is inserted in the uterus

53
Q

What is an example of newborn screening?

A

phenylketonuria- a recessively inherited disorder

Cannot metabolize amino acid phenylalanine

This acid and phenylpyruvate accumulate in the blood and causes mental retardation

If detected early, a special diet low in phenylalanine will allow normal development

BI157 (21 decks)

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