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Praxis (5236) - Biology > 3A3 Genetic Mutations > Flashcards

3A3 Genetic Mutations Flashcards

Describe how genetic mutations occur and their implications. Understand genetic variation and the relationship to cancer.

1
Q

What is meiosis?

A

The halving of chromosomes that occurs within a gamete-producing cell undergoing a cell-division process to form gametes or sex cells.

Also known as reduction division.

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2
Q

What happens during synapsis in meiosis?

A

Homologous chromosomes come together in pairs and form tetrads.

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3
Q

What are nonhomologous chromosomes?

A

Any pair of chromosomes that do not contain the same genetic information in the same order or come from the same parent.

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4
Q

What is crossing over in meiosis?

A

The process where homologous pairs of chromosomes exchange genetic information and alleles, resulting in genetic recombination.

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5
Q

What is a chiasma?

A

The touching of non-sister chromatids from opposite homologous chromosomes in a pair.

Formed during crossing over.

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6
Q

What is recombination?

A

The exchange of genetic information between homologous pairs of chromosomes, leading to genetic variations amongst offspring.

Example: Two parents with heterozygous genotypes for eye color (one blue-eye allele and one brown-eye allele) having a child with blue eyes, despite both having brown eyes.

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7
Q

What are mutations?

A

Any heritable change in a DNA sequence causing changes in RNA and protein sequences.

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8
Q

What is the long-term impact of mutations on species?

A

Can lead to the evolution of new varieties of organisms and contribute to the diversity seen in plants and animals today.

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9
Q

What is a recombination mutation?

A

A mutation resulting from the random exchange of genetic information between homologous pairs of chromosomes during meiosis.

Occurs during crossing over.

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10
Q

What are the different types of mutations that can occur in chromosomes?

A
  • Deletion
  • Duplication
  • Inversion
  • Translocation

Deletion a particular section of a chromosome is lost.

Duplication a particular section of a chromosome is duplicated.

Inversion or switching around of genes or sections that make up a chromosome.

Translocation, which occurs when a portion of a chromosome is detached and reattached to another nonhomologous chromosome.

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11
Q

What is translocation mutation?

A

Occurs when a portion of a chromosome breaks off and reattaches to a separate nonhomologous chromosome during meiosis.

Example: Down Syndrome, infertility, leukemia.

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12
Q

What is the prefix ‘trans’ referring to in translocation?

A

It means ‘across’, indicating the movement of genes from one location to another.

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13
Q

What are the effects of recombination and translocation mutations?

A

Can lead to genetic variation in offspring, but can also result in negative mutations affecting the organism.

Negative effects: genetic death, inability to survive.

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14
Q

What is the difference between recombination and translocation?

A
  • Recombination occurs between homologous pairs.
  • Translocation occurs between nonhomologous pairs.
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15
Q

What are the types of translocations?

A
  • Reciprocal translocations
  • Robertsonian translocations
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16
Q

What occurs during reciprocal translocation?

A

Two different heterologous chromosomes exchange segments of DNA with each other.

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17
Q

What occurs during Robertsonian translocation?

A

An entire chromosome or chromatid can attach to another.

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18
Q

What can happen if an embryo has additional genes or is missing some due to translocation?

A

It is very unlikely that the embryo will survive.

If the embryo does survive, they are extremely likely to have physical abnormalities and cognitive and social learning difficulties.

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19
Q

How can translocation mutations be detected within an organism’s chromosomes?

A

Through a karyotype study.

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20
Q

What is involved in a karyotype study?

A

Creating a micrograph of a complete set of chromosomes from a diploid cell.

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21
Q

What are oncogenes responsible for?

A

Making proteins and contributing to cell growth and cell division.

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22
Q

What can happen if a proto-oncogene becomes an oncogene?

A

It can cause a cell to become cancerous.

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23
Q

What is a mutagen?

A

Any agent in an organism’s environment capable of producing genetic mutations in DNA. This results in the formation of mutations, the primary source of genetic diversity in populations.

Agents can be physical, chemical, or biological.

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24
Q

What does mutagenic mean?

A

The ability to induce genetic changes in the DNA of an organism.

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25
What is DNA composed of?
Monomers called nucleotides, which consist of a phosphate group, pentose sugar, and a nitrogen-containing base.
26
How do mutagens create *damage to DNA*?
By disrupting the normal replication and genetic repair mechanisms.
27
Describe **physical mutagens.**
Different forms of **radiation** that result in the production of free radical damage to DNA. ## Footnote Free radicals cause unintentional bonds to be created between bases of DNA.
28
Describe **chemical mutagens.**
**Compounds** that create direct damage to bases, resulting in base pair mismatching and miscoded regions of DNA. ## Footnote Examples: * Benzene * Tobacco products * Alkaloids
29
Describe **biological mutagens.**
**Viruses and bacteria** that produce DNA damage resulting in cancer formation. ## Footnote Examples: * Human papillomavirus (HPV) * Epstein Barr virus * Hepatitis B, C viruses * Helicobacter pylori * Chlamydia trachomatis
30
What is the role of **DNA polymerase** during DNA replication?
**Builds the daughter DNA strand** along the parent strand, matching nucleotides.
31
How does DNA polymerase **handle errors** during replication?
DNA polymerase *double-checks its work*, stops when it finds an error, and fixes it before replication.
32
How does DNA polymerase **correct mistakes** in DNA replication?
It matches daughter nucleotides to the parent strand and corrects any mistakes through a proofreading step.
33
What happens when **errors** in DNA replication occur?
Mutations persist in the DNA.
34
What are **beneficial mutations**?
They introduce new traits in individuals that *lead to increased fitness or resistance to specific health conditions*, thereby increasing genetic diversity. ## Footnote Also known as advantageous mutations.
35
What are **point mutations**?
These are changes in the nucleotide sequence of DNA that typically **affect one or two bases**, including base substitutions, insertions, and deletions. ## Footnote Common conditions caused by point mutations include: * Cystic fibrosis * Color blindness * Tay-Sachs disease * Sickle-cell anemia * Cancer
36
*How* does a point mutation occur?
Through *natural errors* in replication or through exposure to carcinogens, substances that can cause mutations.
37
What occurs during **base substitution**?
One base switches for another in the DNA sequence. ## Footnote Generally causes relatively minor mutations.
38
What occurs during **insertion**?
A nucleotide is inserted to change the length of the DNA sequence. ## Footnote Can lead to significant mutations.
39
What occurs during a **deletion** mutation?
A base is deleted, changing the length of the DNA sequence. ## Footnote Can lead to significant mutations.
40
What are the **three main types** of point mutations?
* Missense mutations * Nonsense mutations * Silent mutations
41
What is a **missense mutation**?
Occurs when **one of the codons gets replaced by another**, resulting in a different amino acid. ## Footnote An example is sickle cell anemia, where defective red blood cells are produced.
42
What is a **nonsense mutation**?
When a codon is altered to **indicate a premature stop before the protein is complete**, resulting in an incomplete protein.
43
What is a **silent mutation**?
It is when something gets changed on the DNA but it **doesn't impact the organism**.
44
How do **substitution mutations** occur naturally?
During DNA replication, there may be a random mismatch of bases, leading to a change in the sequence at a single base. Mutagens can also chemically alter the nucleotide structure and allow for substitution. ## Footnote Examples of substitution mutations are transversion and transition mutations.
45
What is a **transversion** mutation?
A substitution where a purine is substituted for a pyrimidine, or a pyrimidine is substituted for a purine, changing the structure of DNA. ## Footnote Creates a physical change in the structure of the DNA in addition to changing the bases.
46
What is a **transition** mutation?
A mutation in which the same type of base is substituted. ## Footnote Example: Purine is substitute for purine.
47
What is the **difference** between transition and transversion mutations?
* **Transition**: Same type of base substituted. * **Transversion**: Purine substituted for pyrimidine, or vice versa.
48
What is a **frameshift mutation**?
Occurs during insertion or deletion of multiple bases that are not in multiples of three, affecting the codon reading frame and causing large-scale changes to the protein. ## Footnote Can lead to a large number of altered amino acids.
49
What is the **reading frame** of a gene?
How the nucleotides are partitioned into groups of **three**. ## Footnote Each group of 3 nucleotides is known as a *codon*.
50
What is the **overall effect** of frameshift mutations?
The translational reading frame is "shifted" out of alignment, resulting in a random amino acid sequence. ## Footnote It changes all of the amino acids in the protein, thus altering the protein itself.
51
What are the **two types** of frameshift mutations?
* Insertion Mutations * Deletion Mutations
52
What is the result of **insertion** frameshift mutations?
Shifts the reading frame by **adding extra nucleotide(s)**. ## Footnote The codon where the insertion occurs is affected, as are all subsequent codons. The entire sequence of amino acids after the insertion event is affected.
53
What is the result of **deletion** frameshift mutations?
All codons downstream of the deletion site are affected, and the entire amino acid sequence is changed.
54
What is the **difference** between insertion and deletion frameshift mutations?
* **Insertion** frameshift mutations involve adding one or more nucleotides. * **Deletion** frameshift mutations involve removing one or more nucleotides.
55
Why are frameshift mutations considered harmful?
They affect all the amino acids downstream of their location, leading to a complete loss of function of the gene product in most cases.
56
What are the effects of frameshift mutations?
Complete loss of function for the affected gene; effects vary based on location, number of nucleotides, and combinations. ## Footnote Can lead to various genetic conditions including: * Tay-Sachs Disease * Cystic Fibrosis * Crohn's Disease * Charcot-Marie-Tooth Disease (Hereditary Polyneuropathy) * Hypertrophic Cardiomyopathy
57
How does a frameshift mutation **differ** from missense or nonsense mutations?
* **Frameshift** mutations - changes occur in all the amino acids in the rest of the gene. * **Missense** or **nonsense** mutations - change one amino acid.
58
How do frameshift mutations affect the synthesis of proteins?
They can alter giant portions of proteins, leading to serious defects in the amino acid chain synthesis.
59
When do frameshift mutations have a more dramatic effect?
When they occur in earlier parts of the gene, changing larger portions of the protein.
60
What can **prevent a frameshift mutation** from occurring during an insertion or deletion?
If the segment being inserted or deleted **is three nucleotides long**, the reading frame still lines up properly with all of the codons, preventing a frameshift.
61
Why are frameshift mutations more harmful than substitution mutations?
They affect all subsequent amino acids, not just one.
62
What is an **inversion mutation**?
Occurs when a section of DNA breaks away and reattaches to the chromosome in a **reversed order**. ## Footnote Can lead to diseases such as: * Hemophilia A * Hunter Syndrome
63
What are the **two types** of inversion mutations?
* Paracentric inversion * Pericentric inversion ## Footnote **Paracentric inversion**: occurs when there is a break to only one arm of the chromosome, without involving the centromere. **Pericentric inversion**: occurs when there is a break between two arms of a chromosome, including the centromere.
64
How can inversions be **favorable**?
They prevent recombination and lead to different alleles of the same gene. ## Footnote May allow organisms to acquire traits that are beneficial for their survival.
65
How can an inversion mutation affect the genetic code?
It can make the genetic code change or become more difficult to read, resulting in missing or extra copies of genetic material.
66
What are **somatic cells**?
**Body cells** found everywhere in the body except in places where reproductive cells are produced.
67
What is a **somatic mutation**?
A mutation that occurs in somatic cells throughout the body. ## Footnote Somatic mutations do not affect sex cells (gametes). Examples of diseases caused by somatic mutations include: * Some forms of epilepsy * Cancer
68
What causes **somatic mutations**?
* Internal factors: like errors in DNA replication. * External factors: like mutagens such as ultraviolet radiation.
69
What are **germline cells**?
Cells found in **reproductive organs only**. ## Footnote Examples: Sperm, Egg.
70
What are **germline cell mutations**?
Changes in DNA sequences of cells involved in producing **gametes** (sex cells). These mutations can be passed on to offspring. ## Footnote Examples of diseases caused by germ cell mutations include: * Cystic fibrosis * Color blindness * Sickle cell anemia
71
What is the **difference** between somatic and germline **mutations**?
* **Somatic mutations** are not passed on to the next generation. * **Germline mutations** are spread across generations.
72
What is the **difference** between germline and somatic **cells**?
* **Germline** cells become sex cells. * **Somatic** cells are found in all tissues and organs except those responsible for producing reproductive cells.
73
What is the significance of analyzing a mutation to understand the somatic vs. germline cell mutation risk factor?
It helps calculate the **risk of inheritance** in families with known inherited diseases.
74
What is the difference in **ploidy** between germline and somatic cells?
* **Germline** cells are haploid. * **Somatic** cells are always diploid.
75
What is a **zygote**?
A cell formed by the fusion of gametes during sexual development, which develops into a whole living organism.

Praxis (5236) - Biology (39 decks)

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