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A-level Biology > Module 4 : Genetic Variation And Evolution > Flashcards

Module 4 : Genetic Variation And Evolution Flashcards

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1
Q

What forms the backbone of DNA?

A

Deoxyribose-phosphate backbone

The strands run antiparallel from 5’ to 3’ direction.

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2
Q

Which nitrogenous bases pair complementarily in DNA?

A

Adenine (A), Thymine (T), Cytosine (C), Guanine (G)

A pairs with T, and C pairs with G through hydrogen bonds.

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3
Q

How many hydrogen bonds do A-T and C-G pairs form?

A

A-T pairs form two bonds; C-G pairs form three bonds

This contributes to the overall stability of the DNA molecule.

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4
Q

What is the significance of the double helix structure of DNA?

A

Allows for efficient packing of genetic material

This facilitates replication and transcription processes.

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5
Q

What does the sequence of bases in DNA encode?

A

Genetic information

Crucial for the synthesis of proteins and regulation of cellular activities.

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6
Q

Who discovered the double helix structure of DNA?

A

Watson and Crick in 1953

This discovery was pivotal in understanding genetic inheritance and molecular biology.

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7
Q

What are chromosomes?

A

Structures that organize DNA

Visible during cell division when DNA condenses.

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8
Q

What role do histones play in DNA organization?

A

Help package DNA into a compact, organized structure

Allows for efficient storage and regulation of gene expression.

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9
Q

What state is DNA in during interphase?

A

Relaxed state

Allows for transcription and replication.

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10
Q

What are sister chromatids?

A

Two identical copies of a chromosome joined at a centromere

Ensures accurate distribution of genetic material during cell division.

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11
Q

What is karyotyping?

A

A technique used to visualize chromosomes

Allows for identification of chromosomal abnormalities.

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12
Q

What is the S phase of interphase responsible for?

A

Replication of DNA

Results in two identical sister chromatids.

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13
Q

What is the centromere?

A

The region where sister chromatids are joined

Plays a critical role during cell division.

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14
Q

When are chromosomes visible under a microscope?

A

During cell division

Highlights the dynamic nature of DNA organization.

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15
Q

What is a karyotype used for?

A

Visual representation of an organism’s complete set of chromosomes

Used in genetic analysis and diagnosis of genetic disorders.

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16
Q

What can chromosomal abnormalities lead to?

A

Conditions such as Down syndrome

Caused by an extra copy of chromosome 21.

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17
Q

What are the phases of the cell cycle?

A

Interphase, mitosis, cytokinesis

The cell undergoes these phases to grow and divide.

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18
Q

What occurs during interphase?

A

Cell grows, replicates DNA, prepares for division

Consists of G1, S, and G2 phases.

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19
Q

What is the role of mitosis?

A

Nuclear division ensuring identical set of chromosomes

Follows interphase in the cell cycle.

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20
Q

What happens during cytokinesis?

A

Dividing the cytoplasm and organelles between daughter cells

Results in two genetically identical cells.

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21
Q

Why is regulation of the cell cycle important?

A

Maintains healthy cell growth and prevents uncontrolled division

Uncontrolled division can lead to cancer.

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22
Q

What are the stages of mitosis?

A

Prophase, Metaphase, Anaphase, Telophase

Often remembered by the acronym I.P.M.A.T.

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23
Q

What occurs during prophase?

A

Chromosomes condense, nucleolus disappears, nuclear envelope breaks down

Spindle fibers form from centrioles.

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24
Q

What happens during metaphase?

A

Chromosomes align at the cell’s equator

Spindle fibers attach to the centromeres.

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25
What is the process of anaphase?
Separation of sister chromatids ## Footnote Spindle fibers contract, pulling them to opposite poles.
26
What occurs during telophase?
Nuclear envelopes reform and cytoplasm divides ## Footnote Chromosomes begin to uncoil, completing cell division.
27
What does each daughter cell enter after mitosis?
Interphase with a complete set of DNA ## Footnote Ready for the next cycle of growth and division.
28
What does variation refer to in populations?
Differences in phenotypes among individuals influenced by genetic and environmental factors.
29
How does genetic variation arise?
From mutations, gene flow, and sexual reproduction.
30
What is the concept of a gene pool?
All the genetic information within a population, which can change over time due to evolutionary processes.
31
What is evolution defined as?
The change in inherited characteristics of a population over time, primarily driven by natural selection.
32
Who proposed the theory of natural selection?
Charles Darwin.
33
What does natural selection involve?
Variation, competition, and differential survival.
34
What is speciation?
The process when populations become isolated and evolve independently, resulting in new species.
35
What defines a species?
A group of similar organisms capable of interbreeding to produce fertile offspring.
36
What are the causes of genetic variation?
Mutations, meiosis, and sexual reproduction.
37
What can mutations lead to?
Variations in traits that may affect an organism's survival.
38
What is a mutation?
A change in the DNA base sequence that can alter genetic information.
39
What types of mutations exist?
* Substitutions * Deletions * Insertions
40
What is a base substitution?
Replacing one base with another in the DNA sequence.
41
What are frameshift mutations?
Mutations caused by insertions or deletions that alter the reading frame.
42
What are mutagenic agents?
Physical or chemical factors that increase the frequency of mutations.
43
What is the genetic code?
The set of rules by which information encoded in DNA is translated into proteins.
44
What does the degeneracy of the genetic code mean?
Multiple codons can code for the same amino acid.
45
What does non-disjunction refer to?
The failure of chromosomes to separate properly during cell division.
46
What genetic disorders are associated with non-disjunction?
* Down syndrome * Turner syndrome * Klinefelter syndrome
47
What is an example of a harmful mutation?
Cystic fibrosis caused by a single substitution mutation.
48
What role do mutations play in evolution?
Provide genetic diversity that can confer survival advantages.
49
What is meant by 'survival of the fittest'?
Those best adapted to their environment are more likely to survive and reproduce.
50
What is the impact of spontaneous mutations?
They occur naturally and contribute to genetic diversity.
51
How do mutagenic agents affect mutation rates?
They increase the likelihood of mutations occurring.
52
Would mutations still occur without mutagenic agents?
Yes, because spontaneous mutations can occur.
53
What is a substitution mutation?
A mutation where one base is replaced with another.
54
What type of mutation can result in large changes to the amino acids coded for?
Frameshift mutations.
55
What is an example of a non-coding section of a gene?
Introns.
56
What is the significance of studying genetic variations?
It is crucial for understanding genetics, medicine, and evolutionary biology.
57
What are gametes?
Reproductive cells involved in sexual reproduction ## Footnote Female gametes are called ova or egg cells, while male gametes are called sperm. Each gamete is haploid.
58
What is the definition of haploid?
Contains only one set of chromosomes ## Footnote Crucial for maintaining the chromosome number across generations.
59
What are homologous chromosomes?
Pairs of chromosomes with the same structural features and genes at the same loci, but may have different alleles.
60
What are chromatids?
Cloned sections of chromosomes formed during DNA replication, held together at a centromere.
61
What is the difference between haploid and diploid cells?
Haploid cells contain a single set of chromosomes (n), while diploid cells contain two sets (2n).
62
How many chromosomes do human gametes contain?
23 chromosomes ## Footnote Somatic cells are diploid and contain 46 chromosomes.
63
What is meiosis?
A specialized type of cell division resulting in four haploid daughter cells.
64
What are the two main stages of meiosis?
Meiosis I and Meiosis II.
65
What occurs during Meiosis I?
Separation of homologous chromosomes.
66
What occurs during Meiosis II?
Separation of sister chromatids.
67
What is independent assortment?
The random distribution of homologous chromosomes during meiosis I.
68
What is crossing over?
The exchange of genetic material between homologous chromosomes during prophase I.
69
Why is meiosis important for sexual reproduction?
It produces gametes essential for restoring the diploid state in the zygote.
70
What are the key differences between mitosis and meiosis?
Mitosis results in two genetically identical cells; meiosis results in four genetically diverse haploid cells.
71
What role does recombination play in meiosis?
Exchanging genetic material between homologous chromosomes, leading to new allele combinations.
72
What is an allele?
Different versions of the same gene that code for the same protein but may have different forms.
73
What is a locus?
The specific location of a gene on a chromosome.
74
What is the significance of genetic variation?
Fundamental for evolution and adaptation in populations.
75
What is the estimated number of possible combinations of chromosomes in human gametes due to independent assortment?
2^23 (over 8 million).
76
What are chiasmata?
Points of exchange during crossing over.
77
How does the distance between genes affect crossing over?
Genes that are far apart are more likely to undergo crossing over than those that are close together.
78
What is the role of meiosis in the life cycles of organisms like ferns and mosses?
Produces haploid spores through meiosis, while gametes are formed via mitosis.
79
Fill in the blank: Meiosis consists of two main stages: _______ and _______.
Meiosis I, Meiosis II

A-level Biology (8 decks)

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