Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > Ch 12 - Genetics & Evolution > Flashcards

Ch 12 - Genetics & Evolution Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What is a chromosome?

A

What all genes are arranged into

This is to ensure that all genetic material is passed on from mother to daughter cell during mitosis and meiosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are alleles?

A

Alternative forms of a gene

Emailed: ABO blood group has three alleles for the same gene (Ia, Ib, i)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a genotype?

A

The genetic combination that an individual has

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a phenotype?

A

The MANIFESTATION of of a given genotype via observable traits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are homologues?

What is the one exception to this?

A

Homologues are two copies of each chromosome - humans have 2 copies of each chromosomes.

The exception is the male sex chromosome which has one X chromosome and one Y chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the LOCUS of a chromosome?

A

A specific place for the gene to be

The normal locus of each gene is the same among all humans, so that a gene can be found based on the description of it’s location

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Since there are two of each chromosome, what does this mean for alleles?

A

There are hence two alleles present for each gene.

These can be the SAME allele - HOMOZYGOUS

Or can be two different alleles - HETEROZYGOUS

HEMIZYGOUS means that only one allele is present for a given gene, for example the X chromosome in men

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are alleles categorized based on?

Dominant versus Recessive

A

Based on their expression (via phenotype)

Dominant: if only one copy of an allele is needed to express a phenotype

Recessive: if two copies of the allele are needed to express a phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is complete dominance?

A

When there is one dominant allele and one recessive allele

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is co dominance?

A

Two dominant alleles

Ie: someone with an allele for A antigen and an allele for B antigen = AB blood type

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is incomplete dominance?

A

No dominant alleles

When a heterozygote (two diff alleles) express a phenotype that is intermediate between the two homozygous genotypes

Ie: a red flower with a white flower = a pink flower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is penetrance?

A

A population measure

The proportion of people in a population who carry the allele and express the phenotype

(Given that someone has the allele, the likelihood that they will express the phenotype)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

An example of penetrance

Huntington’s disease

A

People with 40 sequence repeats have FULL PENETRANCE meaning that 100% of individuals with this allele show symptoms.

Fewer sequence repeats: HIGH penetrance, aka most but not all of the people who have this allele will express the disease

With fewer sequence repeats, the gene has REDUCED PENETRANCE aka very few people with the allele express the phenotype

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is expressivity?

A

On the individual level. The different manifestations of the same genotype.

Varying PHENOTYPE despite identical GENOTYPE

It is either CONSTANT (given genotype always results in one phenotype) or VARIABLE (same genotype but different phenotypes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a gene?

A

A DNA sequence that codes HERITABLE TRAITS that can be passed from one generation to the next

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Four tenets of Mendel’s first law of SEGREGATION

A
  1. Genes exist in alternate forms (alleles)
  2. Two alleles for each gene (one from each parent)
  3. Two alleles segregate during meiosis, making gametes that have only 1 allele for any inherited trait
  4. Two diff alleles means one will be silent and one will be fully expressed (dominant and recessive) *with the exception of complete and co- dominance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Mendel’s first law (of segregation) applies to which phase of meiosis

A

Anaphase 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What genetic material (re: alleles) does each gamete carry ?

A

ONE ALLELE for any given trait

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What do segregation and independent assortment lead to in gametes?

A

GENETIC DIVERSITY of the gametes and eventually of the offspring as well

Imrpove ability of a species to evolve and adapt to environmental stresses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why phases of meiosis do Mendel’s first and second laws most closely take place?

A

Mendel’s first law (segregation) - Anaphase 1

Mendel’s second law (independent assortment) - Prophase 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Mendel’s second law of INDEPENDENT ASSORTMENT

What is it

How does it happen

A

The inheritance of one gene does NOT affect the inheritance of another

This happens during PROPHASE if meiosis 1, where a tetras is created by homologous chromosome pairs. (2 chromatids in each of the chromosomes)

RECOMBINATION takes place, swapping of small segments of emetic material - results in novel combinations of alleles that were not present in the original chromosomes.

*recent findings of LINKED GENES make this theory questionable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is a gene pool?

A

All of the alleles that exist within a species.

Mutations, genetic leakage, and genetic drift allow the species to evolve and adapt to environments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a mutation?

Give 3 examples

A

A change in DNA sequence

Ionizing radiation (can damage DNA)

DNA polymerase can make mistakes during DNA replication (proof reading mechanisms help prevent this)

Transposons (can insert and remove themselves from the genome)
*transposon going into the MIDDLE of a code can disrupt the gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are other ways that flawed proteins can happen, unrelated to damage in DNA?

A

Indirectly pairing nucleotides during transcription and translation

tRNA put with incorrect amino acid for it’s anticodon

(These cause de arrangements to the normal amino acid sequence)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are point mutations?

3 examples

A

Occur when one nucleotide is swapped for another (A, T, C, G)

Silent (no change in amino acid)
Missense (diff amino acid)
Nonsense (results in STOP codon)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are frameshift mutations?

A

When nucleotides are added or deleted from the genome (and shift everything over by one)

“Insertion” or “deletion” frameshift mutations

Results in either a change in the amino acid sequence, or truncating of the protein due to a nonsense mutation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is a chromosomal mutation?

5 types

A

On a larger scale - affects large segments of DNA

Deletion
Duplication
Inversion
Insertion (DNA from another chromosome)
Translocation (swapped segment of DNA between chromosomes)
27
Q

How can mutations be advantageous?

A

If the mutation has few side effects but some resistance to something

Ie, people who are heterozygotes for sickle cell disease have minor symptoms but have natural resistance to malaria because their RBC’s have a slightly shorter lifespan (short enough that malaria can’t reproduce)

28
Q

What are inborn errors of metabolism?

A

A class is deleterious mutation (detrimental = bad!)

Where the defects affect the genes requires for metabolism - results in a buildup of metabolite a in various pathways

29
Q

What is genetic leakage?

A

Two species that are closely related but different, could mate

Example: donkey
Has 63 chromosomes so actually cannot mate! (Cannot form homologous pairing in meiosis hence can’t form gametes)

Example: beefalo CAN reproduce with either cattle or bison which is what it is a hybrid of.

30
Q

What is genetic drift?

A

Changes in the composition of the gene pool DUE TO CHANCE

More pronounced in small populations

Founder effect (isolation from other populations)

Bottleneck effect (when the population gets really small)

Both tend to result from a catastrophic or environments effect

THESE ALL REDUCE GENETIC DIVERSITY and as a result, certain populations may have increased prevalence of certain traits or diseases

31
Q

What is inbreeding depression?

What ca be introduced to reverse it?

A

Reduced fitness in the population

OUTBREEDING or OUTCROSSING aka introducing new unrelated individuals into the group could result in increases variation in a gene, and increases fitness in the population

32
Q

What is the result of crossing two heterozygotes with complete dominance?

A

1: 2:1 ratio of genotype
3: 1 ratio of phenotypes (dominant:recessive)

(Homozygous dominant; heterozygous dominant; homozygous recessive)

This is not “always” true, especially not in smaller populations.

The more children that parents have, the more the phenotypic ratios hold true

33
Q

What is a di-hybrid cross?

A

Looks at the inheritance of two different genes

According to Mendel’s second law (of independent assortment) the genes are independent of each other (except for linked genes)

35
Q

What is the phenotypic ratio for di-hybrid crosses between 2 heterozygotes with complete dominance ?

A

9:3:3:1

(One each for different possible gene combinations: XY, Xy, xY, xy)

The 3:1 phenotypic ratio still holds for each trait

36
Q

How is a sex-linked trait different?

A

Females: two X chromosomes
(Homozygous)
Males: one X and one Y
(Heterozygous)

Always assume sex-linked trais are RECESSIVE (needs two copies of an allele to express phenotype - therefore XX and XY are used)

Males are HEMIZYGOUS for many genes carried on the X chromosome. Hence sex linked traits are more common in males –> having only one recessive allele is sufficient for expression of the recessive phenotype

37
Q

Facts about males and genetics

  • who determines sex of offspring?
  • can man pass down a sex-linked trait (diseased) to his son?
A

Sperm determines the sex of a child
(Because the egg carries an X chromosome)

A man can’t pass down a sex linked trait to his son, though it can be passed down to daughters (who are then “carriers”

38
Q

What happens to alleles during Prophase 1 of meiosis?

A

Crossing over causes alleles to be swapped between homologous chromosomes (this is Mendel’s second law)

39
Q

Which genes are most likely to swap and which are least likely to?

A

Genes that are very close to each other are less likely to be separated during crossing over - the further apart the news are from each other, the more likely they are to cross over

40
Q

What is a CHIASMA?

A

A point of crossing over

41
Q

What is recombination frequency ?

0-not

A

The likelihood that two alleles are separated from each other during crossing over

This is proportional to the distance between genes on a chromosome.

Tightly linked genes: close to 0% recombination frequency

Weakly linked genes: about 50% recombination frequency

42
Q

How does recombination frequency relate to genetic mapping?

A

Recombination frequency can help create a genetic map by govongn relative distances between genes.

1 map unit (centimorgan) is a 1% chance of recombination.

With known frequencies between genes, we can deduce te order of the genes on the chromosome because map units are additive

43
Q

What is allele frequency?

How is evolution related to this idea?

A

How often an allele appears in a population

Evolution results from changes to gene frequencies in reproducing populations over time

No change in gene frequency = NO EVOLUTION!

44
Q

How might the gene (allele) frequency NOT be changing ?

5

A
  • very large population (no drift)
  • no mutations that affect gene pool
  • mating is random (no selection)
  • no migration of individuals in or out of the population
  • genes are all equally successful at reproducing
45
Q

What is Hardy-Weinberg equilibrium?

Theory

A

Given that the 5 conditions are met for the gene frequency of a population NOT changing.

If the conditions are met, and the population is in Hardy-Weinberg equilibrium, a pair of equations can calculate the allele and phenotype frequencies

46
Q

What are the Hardy-Weinberg equations?

A

Frequency of alleles in the population
p + q = 1

Frequency of genotypes/phenotypes in the population
p^2 + 2pq + q^2 = 1

Where p is the frequency of the dominant allele (T) and q is the frequency of the recessive allele (t)

If we know p or q we can calculate everything else!

48
Q

What is a test cross used for?

A

Used to determine an unknown genotype

(Sometimes called back-crosses)

Unknown type is crossed with a KNOWN homozygous recessive

49
Q

What is natural selection?

A

“Survival of the fittest”

Individuals with heater reproductive success tend to pass on those genes to offspring

50
Q

Charles Darwin’s natural selection theory was based on these tenets:
(3)

A
  • few offspring survive to reproductive maturity
  • chance variations are FAVORABLE when they give the animal a survival advantage
  • more favorable traits –> more likely to survive, increasing these traits in future generations. Reproductive success is called FITNESS
51
Q

What is the modern synthesis theory / neo-Darwinism?

A

Adds new knowledge about emetic inheritance and changes to gene pool (mutation, recombination)

52
Q

What is differential reproduction?

A

When changes (mutations, drift) are favorable to an organisms survival they are more likely to be passed on - the opposite is also true.

53
Q

What is inclusive fitness?

A

A measure of an organisms success in a population

54
Q

What is punctuated equilibrium?

A

Contrast to Darwin’s theory, suggests that changes in some species occur in rapid bursa rather than evenly over time (observed in fossils)

55
Q

3 modes of natural selection:

A
  1. Stabilizing
  2. Directional
  3. Disruptive
56
Q

What is stabilizing natural selection?

A

Keeps phenotypes within a specific range by selecting AGAINST extremes

Ie human birth weight

57
Q

What is directional natural selection?

A

When an extreme survives

“Differential survivorship” ie resistant bacteria –> antibiotics kill all that aren’t resistant, so only resistant remain.

58
Q

What is disruptive natural selection?

A

TWO extreme we phenotypes are selected over the norm.

Darwin’s finches, all had small or large beaks, no mediums.

59
Q

What is adaptive radiation?

A

Describes the rapid rise of a number of different species from a common ancestor

Allows various species to occupy different NICHES (specific ways of life) decreasing competitor for limited resources.

60
Q

What are species?

What is speciation?

A

Species are he largest group or organisms capable of reproducing to produce an offspring.

Speciation is the creation of new species through evolution

61
Q

What is isolation?

A

Take two identical species and isolate the geographically for long periods of time - eventually he progeny can no loner freely interbreed. The two groups hence become different species.

62
Q

What are two types of reproductive isolation?

A

Pre-zygotically

Post-zygotically

63
Q

Pre-zygotic reproductive isolation:

A

Prevents formation of the zygote altogether

Includes:
Temporal isolation 
Ecological isolation
Behavioral isolation
Reproductive isolation 
Gamete isolation
64
Q

Post-zygotic reproductive isolation:

A

Allows gametes to fuse but girls a non viable or sterile offspring.

Includes:
Hybrid inviability (can’t make it)
Hybrid sterility
Hybrid breakdown (first gen ok but second gen breakdown)

65
Q

What is divergent evolution?

A

Independent development of different characteristics in a lineage that shares a common ancestor.

Diff environment, diff selection, same ancestors

Ie, seals and cats are both mammals

66
Q

What is parallel evolution?

A

Related species evolve in similar ways in response to selection.

Same environment, same selection, same ancestors

67
Q

What is convergent evolution?

A

Indecent development of similar characteristics in lineages NOT sharing an ancestor.

Same environment, same selection, DIFF ancestors

Ie: fish and dolphins

68
Q

What is the molecular clock model?

A

The theory that the amount of time since species split from each other is directly related to the similarity of the genome.

Species that recently split off from the same common ancestor will have a higher degree of genomic similarity (ie chimpanzees share 95% of their genome with humans)

Biology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions