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Chapter 10 Flashcards

Patterns of Inheritance (58 cards)

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1
Q

How can genetics explain and predict inheritance patterns?

A

-a gene is a segment of DNA that carries the instructions for synthesizing a protein
-genetics can explain why these children look different
-analyzing their genes can also help predict the appearance of their offspring

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2
Q

How can genetics determine body functions and health?

A

-most genetics encode proteins that have nothing to do with outward appearance
-the enzymes essential to our loves are also the product of genetics
-studying genetics also allows scientists to breed superior crops and doctors to track genetic illnesses

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3
Q

What are chromosomes?

A

-they are packets of genetic information
-recall that a chromosome is a piece of DNA containing many different genes
-when 2 haploid cells fuse during fertilization, a diploid zygote with two full sets of chromosomes is formed

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4
Q

Define locus

A

-a genes physical location on a chromosome

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5
Q

Chromosomes are paired into…?

A

-diploid cells
-each chromosome is a member of a homologous pair
-humans have 22 homologous pairs of autosomes and one pair of sex chromosomes

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6
Q

How many alleles do diploid cells have per gene?

A

-they have 2 alleles per gene
-members of a homologous pair have the same genes but might have different versions (alleles) of those genes

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7
Q

Are sex chromosomes homologous?

A

-female sex chromosomes are homologous (XX)
-male sex chromosomes are not homologous (XY)

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8
Q

Gregor Mendel uncovered basic laws of inheritance

A

-gregor mendel used pea plants to study heredity
-hand pollinating the plants allowed mendel to control plant breeding experiments
1.) pollen from tall plant is transferred to flower on short plant
2.) pods contain the offspring (seeds) resulting from the cross
3.) seeds are planted
4.) each seed develops into a short or tall plant

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9
Q

Define homozygous

A

-they are true breeding because all of the gametes contain the same allele
-has 2 identical alleles for a particular gene (YY or yy)

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10
Q

Define heterozygous

A

-they are not true breeding because they pass on either a dominant or recessive allele (hybrid)
-produces a mix of offspring for one or more traits
-has 2 different alleles for a particular gene Yy)

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11
Q

Define wild type

A

-the most common allele, genotype or phenotype in a population

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12
Q

Define mutant

A

-an allele, genotype, or phenotype that is not most common in a population or has been altered from the typical (wild type) condition
-when a gene has undergone a mutation

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13
Q

What is the order of the generations P, F1, and F2?

A

1.) P generation (parental) is the first generation (true breeding)
2.) F1 generation if the offspring of P generation
3.) F2 generation is the offspring of F1 generation in a genetic cross

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14
Q

Define true breeding

A

-self fertilization yields offspring with the same seed color (homozygous) as parent plant
-true breeding plants produce offspring identical to themselves (in one or more traits)

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15
Q

Define hybrid

A

-self fertilization yields a mix of seed colors
-hybrid plants outwardly resemble true breeders but produce mixed offspring

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16
Q

Define dominant allele

A

-dominant alleles express their effects wherever they are present
-crossing a yellow seed plant with a green seed plant will always yield some yellow seeds (yellow seed color is therefore dominant)
-active allele and produces yellow color by encoding a pigment metabolizing enzyme

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17
Q

Define recessive allele

A

-a recessive allele, like green seed color, is whose effect is masked if dominant allele is also present
-recessive alleles usually encode nonfunctional proteins
-inactive allele
-in the absence of pigment metabolizing enzymes, the seed color stays green

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18
Q

Why do some plants produce both yellow and green seeds?

A

-the answer has to do with each plant having 2 alleles for each gene
-because of their homologous pair of chromosomes

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19
Q

Define genotype

A

-it represents an individuals 2 alleles for one gene
-the genotype confers the phenotype (the physical appearance)

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20
Q

Define phenotype

A

-the physical appearance of the offspring
-look at the offspring to determine the genotype of the parent
-individuals with the same phenotype can have different genotypes

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21
Q

What does a Punnett square do?

A

-it represents gamete formation and fertilization
-a punnett square uses the genotypes of the parents to reveal which alleles the offspring may inherit
-it shows how alleles separate during meiosis

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22
Q

Define a monohybrid cross

A

-a female parent heterozygous for seed color is crossed with a male parent who is also heterozygous for seed color
-this is a monohybrid cross because both parents are heterozygous

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23
Q

Define test cross

A

-the mating of an individual with unknown genotypes to a homozygous recessive individual to reveal the unknown genotype

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24
Q

Define the law of segregation

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A

-mendel’s law stating that the 2 alleles of each gene are packaged into separate gemetes

25
Define dihybrid cross
-mating between 2 individuals that are heterozygous for 2 genes
26
Dihybrid cross track the inheritance of 2 genes at once
-alleles separate during meiosis -based on dihybrid crosses, mendel proposed the law of independent assortment
27
Define the law of independent assortment
-the segregation of alleles for 1 gene doesn't influence the segregation for another gene
28
Define the product rule
-tracking 2 or more genes on 1 punnett square is challenging and time consuming -this rule simplifies it by multiplying the individual probabilities together -the probability of an offspring inherits the genotype Rr Yy Tt = the probability of Rr x the probability of Yy x the probability of Tt -(1/2) X (1/2) X (1/2) = 1/8
29
Define linked genes
-genes on the same chromosome
30
Punnett squares and the product rule assumes 2 genes are assorted independently
-when genes are linked, they are physically near each other -therefore, they not not sort independently -the linked genes are not inherited independently to each other -punnett squares and the product rule can't be used if genes are linked, because inheriting 1 allele influences the likelihood of inheriting a linked gene
31
Define crossing over
-an exchange of genetic material between homologous chromosomes during prophase I of meiosis -afterwards, no 2 chromatids on a homologous pair of chromosomes are identical
32
Genes can be 'unlinked' during crossover
-crossing over physically separates the 2 genes loci onto 2 different chromosomes
33
Very close genes are less effected by crossing over
-the probability of a crossover event between 2 linked alleles is proportional to the distance between the genes -the farther apart the genes are, the higher the chance of crossing over -crossover events are counted by tallying offspring in which the genes are inherited separately
34
Define linkage map
-a diagram of gene order an spacing on a chromosome, based of crossover frequencies
35
Define linage group
-a group of genes that tend to be inherited together because they are on the same chromosome
36
Define incomplete dominance
-alleles do not mask each other -the heterozygote has an intermediate phenotype (a blend) -red allele doesn't mask the white allele, instead it turns pink
37
Define codominance
-alleles do not mask each other -the heterozygotes show both phenotypes -more than one allele encodes a functional protein -human blood A and B are codominant, which makes the blood type AB
38
Define plietrophy
-a single gene effects multiple, seemingly unrelated phenotypes -1 gene has multiple effects on the phenotype -a gene might affect more than 1 biochemical pathway -ex: Marfan Syndrome
39
Define epistasis
-interaction in which 1 gene masks the phenotype associated with another gene -occurs when one genes product affects the expression of another gene
40
What is the percent of chance that offspring will be male or female?
-always 50% chance male and 50% chance female
41
Which gamete will determine the sex of the offspring?
-the egg will always carry the X chromosome -the sex chromosome in sperm will determine if offspring is male or female
42
Why do X-linked recessive disorders affect more males than females?
-males only need to inherit 1 X-linked recessive allele to express the recessive disorder -females must receive both recessive alleles on both X chromosomes to express the recessive disorder, which is less likely to occur
43
What does X inactivation do?
-it prevents double dosing of gene products -each cell in XX individuals, such as females, randomly inactivate 1 X chromosome early in development -it is random which X gets inactivated
44
X-linked dominant disorders are less severe in females
-in humans, X-linked disorder called Rett syndrome is lethal to boys and has varying effects of girls, depending on how many cells inactivate the X chromosome carrying the X allele
45
Define sex linked
-describes genes or traits on the X or Y chromosome
46
Define Y linked
-describes traits controlled by genes on the Y chromosome -fewer than 100 genes
47
Define X linked
-describes traits controlled by genes on X chromosome -more than 1,000 protein encoding genes
48
Define pedigree
-a chart showing family relationships and phenotypes -shows modes of inheritance -tracks an autosomal recessive disorder -tracks an X-linked recessive disorder (more males are affected)
49
Define autosomal dominant
-inheritance pattern of a dominant allele on an autosome
50
Define autosomal recessive
-inheritance pattern of a recessive allele on an autosome
51
How can the environment alter a phenotype?
-many genes are effected by the environment -for example, the enzyme responsible for pigment production in Siamese cat fur is active only in cool body parts (enzyme active) -in warm body parts, no color is produced (enzyme inactive)
52
Define epigenetics
-the study of changes in gene expression that don't involve changes in DNA sequence -environment can alter phenotypes through epigenetics -it is a field of research that explores how cells adjust gene expression without altering underlying DNA sequence -differences in lifestyle and experience can epigenetically influence gene expression and alter the chances of cancer, depression, alcoholism, and type 2 diabetes
53
Define polygenic
-caused by more than 1 gene -polygenetic traits are typically expressed as a continuum of possible phenotypes -skin color is a polygenetic trait because it is caused by more than 1 gene
54
Investigating life: BT toxins kill of bollworms
-bollworm larvae devastate cotton crops, but some bollworms are susceptible to BT toxin -biologists have inserted the gene encoding this toxin into genome, to kill off bollworms that try to eat the cotton
55
Investigating life: some bollworms are resistant
-BT toxin kills the susceptible bollworms, leaving the resistant bollworms to survive and reproduce -after several generations, there are few susceptible bollworms in the population, and BT cotton becomes ineffective
56
Investigating life: BT resistant is a recessive allele
-in a mating between 2 BT resistant bollworms, all offspring will also be resistant -however, if a resistant bollworm, only some (and sometimes none) of the offspring will be resistant
57
Investigating life: the buffer-refuge strategy
-to avoid 100% resistance among bollworms, farmers plant "buffer" crops lacking the BT toxin -this removes the selective pressure for resistance to BT -the resistant allele becomes less frequent in the bollworm population
58
Investigating life: the 2 toxin strategy
-to further decrease resistance among bollworms, companies have developed a second toxin -bollworms that are resistant to BT toxin can't survive in cotton that produces both toxins

Principles of biology (12 decks)

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