DNA and Inheritance

Question 1

What is meiosis?

Answer 1

Meiosis is the process of cell division that produces gametes, resulting in four non-identical haploid daughter cells.

Question 2

How many divisions occur in meiosis?

Answer 2

Meiosis involves two divisions: meiosis I and meiosis II.

Question 3

What happens in meiosis I?

Answer 3

In meiosis I, homologous chromosomes separate, resulting in two cells with one chromosome (consisting of two chromatids) per chromosome pair.

Question 4

What occurs during prophase I of meiosis?

Answer 4

Prior to prophase I, chromosomes replicate to form sister chromatids. During prophase I, the nuclear envelope disintegrates, chromosomes condense, and spindle fibers appear.

Question 5

How many chromatids and chromosomes are present in each pair during prophase I?

Answer 5

During prophase I, there are initially four chromatids (4c) and two chromosomes (2n) for each of the 23 chromosome pairs.

Question 6

What is the significance of spindle fibers in meiosis?

Answer 6

Spindle fibers play a crucial role in ensuring the successful division of chromosomes during meiosis.

Question 7

What is crossing over in meiosis?

Answer 7

Crossing over is the process in meiosis where homologous chromosomes exchange small parts of themselves, resulting in one chromosome containing both maternal and paternal DNA.

Question 8

What are chiasmata?

Answer 8

Chiasmata are the points at which crossing over occurs on a chromosome during meiosis.

Question 9

What happens during metaphase I of meiosis?

Answer 9

In metaphase I, homologous chromosomes align along the equator of the cell. Independent assortment occurs, where maternal and paternal chromosomes randomly line up on either side of the equator.

Question 10

What is independent assortment?

Answer 10

: Independent assortment is the process during metaphase I of meiosis, where maternal and paternal chromosomes randomly align themselves on either side of the equator. This leads to genetic diversity among offspring.

Question 11

How does independent assortment contribute to genetic diversity?

Answer 11

Independent assortment during meiosis leads to different combinations of maternal and paternal chromosomes being allocated to gametes, resulting in genetic diversity among offspring.

Question 12

What happens during anaphase I of meiosis?

Answer 12

In anaphase I, homologous chromosomes separate and are pulled towards opposite poles of the cell as the spindle fibers retract. This divides the DNA equally between the two cells that will be formed.

Question 13

What occurs during telophase I of meiosis?

Answer 13

During telophase I, the nuclear envelope reforms, and the spindle fibers disappear. This marks the end of the first division of meiosis.

Question 14

What is cytokinesis I?

Answer 14

Cytokinesis I is the process of dividing the cytoplasm and the cell after telophase I of meiosis. It results in the formation of two technically haploid cells, each containing one chromosome and two chromatids for each chromosome (2c, n).

Question 15

How does cytokinesis I contribute to the formation of haploid cells?

Answer 15

Cytokinesis I completes the separation of the chromosomes into two cells, resulting in the formation of technically haploid cells in which the chromosome number is halved.

Question 16

What happens during prophase II of meiosis?

Answer 16

Prophase II in meiosis II is similar to prophase I, where the nuclear envelope disintegrates, and the chromosomes condense.

Question 17

What occurs during metaphase II of meiosis?

Answer 17

In metaphase II, chromosomes line up in single file along the equator of the cell, unlike metaphase I where they line up in homologous pairs.

Question 18

What happens during anaphase II of meiosis?

Answer 18

In anaphase II, sister chromatids are pulled to opposite poles of the equator.

Question 19

What is telophase II in meiosis?

Answer 19

Telophase II is similar to telophase I, where the nuclear envelope reforms, and the spindle fibers disappear.

Question 20

What is cytokinesis II?

Answer 20

Cytokinesis II is the process of dividing the cytoplasm and the cell after telophase II of meiosis. It results in the formation of two non-identical haploid daughter cells, each containing one chromosome consisting of one chromatid (1c, 1n).

Question 21

How many non-identical haploid daughter cells are produced at the end of meiosis II?

Answer 21

At the end of meiosis II, four non-identical haploid daughter cells are formed, each containing one chromosome consisting of one chromatid (1c, 1n). These daughter cells are fully formed gametes.

Question 22

What are recombination errors and what can they lead to?

Answer 22

Recombination errors during meiosis can result in gene duplications or loss, as well as inversions and translocations.

Question 23

What is non-disjunction in meiosis?

Answer 23

Non-disjunction is the failure of homologous chromosomes or sister chromatids to separate properly during meiosis, leading to an abnormal distribution of chromosomes in the resulting gametes.

Question 24

What can non-disjunction in meiosis result in?

Answer 24

Non-disjunction can give rise to conditions such as trisomy (an extra chromosome) or monosomy (a missing chromosome).

Question 25

Which chromosomes are exceptions to the usually fatal outcome of trisomy or monosomy?

Answer 25

Chromosomes 13, 18, and 21, as well as the sex chromosomes, can tolerate trisomy or monosomy to some extent.

Question 26

What is the consequence of non-disjunction of sex chromosomes?

Answer 26

Non-disjunction of sex chromosomes is generally better tolerated compared to autosomal non-disjunction. It can often be diagnosed at puberty or as a result of fertility issues.

Question 27

What is Turner Syndrome, and what are its characteristics?

Answer 27

Turner Syndrome is a condition in females characterized by having only one X chromosome (XO). It is associated with reduced height, underdeveloped ovaries, and may include features such as neck webbing, heart, and kidney defects.

Question 28

What is Klinefelter syndrome, and what are its characteristics?

Answer 28

Klinefelter syndrome is a condition in males characterized by having an extra X chromosome (XXY). It can result in reduced fertility and may affect general development.

Question 29

What is DNA damage?

Answer 29

DNA damage refers to any change in the DNA sequence, whether it is large or small, beneficial or harmful. It can occur in the germline (cells that give rise to gametes) or the soma (non-reproductive cells).

Question 30

What are mutations?

Answer 30

Mutations are changes in the DNA sequence and are the source of all genetic variation. They can occur randomly and can be harmful, neutral, or advantageous. Generally, mutation rates are low.

Question 31

How is DNA repair carried out?

Answer 31

DNA repair involves several major routes. Firstly, polymerases involved in DNA replication have 3’-5’ exonuclease activity, allowing proofreading and correction of errors during replication. Additionally, base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR) systems act throughout the cell’s life to repair DNA damage. There is also a specific system that repairs double-stranded breaks, which is related to the recombination system.

Question 32

What is proofreading in DNA replication?

Answer 32

During DNA replication, polymerases have 3’-5’ exonuclease activity, allowing them to proofread and correct errors made during replication, thereby increasing the accuracy of DNA synthesis.

Question 33

What are some examples of DNA repair systems?

Answer 33

Base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR) are three systems involved in repairing DNA damage. They operate throughout the life of the cell and help maintain the integrity of the DNA sequence.

Question 34

What is the specific system involved in repairing double-stranded breaks?

Answer 34

There is a specialized system that repairs double-stranded breaks in DNA, which is related to the recombination system. It ensures the accurate repair of breaks and helps maintain genomic stability.

Question 35

What are mitochondrial diseases?

Answer 35

Mitochondrial diseases are a group of disorders caused by mutations in mitochondrial genes. These mutations are often maternally inherited and can result in a range of diseases.

Question 36

What is Leber’s hereditary optic atrophy (LHON)?

Answer 36

LHON is a mitochondrial disease characterized by midlife, acute or subacute, painless central vision loss. It is caused by various mutations in mitochondrial DNA (mtDNA).

Question 37

What is Myoclonic epilepsy with ragged red fibers (MERRF)?

Answer 37

MERRF is a mitochondrial disease where the majority of cases (80-90%) are caused by an A->G mutation at nucleotide 8,344 in mtDNA. This mutation leads to a defect in the translation of all mtDNA-encoded genes and results in symptoms such as myoclonic seizures and muscle weakness.

Question 38

What is Cystic Fibrosis?

Answer 38

Cystic Fibrosis is a genetic disease caused by mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. The mutations can result in a dysfunctional CFTR protein, leading to impaired chloride ion transport in epithelial tissues. This affects various organs, including the lungs, pancreas, and digestive system.

Question 39

What are the types of mutations in Cystic Fibrosis?

Answer 39

Mutations in the CFTR gene associated with Cystic Fibrosis can be in the form of blocked channels or fewer channels on the membrane surface, resulting in impaired chloride transport.