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Biology > 9.4 > Flashcards

9.4 Flashcards

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1
Q

What are genes?

A

Regions that the DNA on chromosomes is arranged in; they code for the formation of proteins, which carry out most of the work of cells.

Each chromosome consists of hundreds of genes, each playing a role in determining the characteristics and functions of the cell.

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2
Q

How many chromosomes does each human cell have?

A

Human body cells have 46 chromosomes, except for gametes. Each parent contributes 23, resulting in 23 pairs of chromosomes.

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3
Q

What are homologous chromosomes?

A

They are Chromosomes that make up a pair, each piece from a parent. Homologous chromosomes have the same length and centromere position and carry genes that control the same traits.

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4
Q

What are Gametes?

A

They are sex cells that have a single set of chromosomes.

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5
Q

What does the symbol n represent?

A

It represents the number of chromosomes that each parent contributes to a cell or the number of chromosomes in a single set. In humans, n is 23.

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6
Q

What is a haploid cell?

A

A cell that has only one set of (or n) chromosomes.

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7
Q

What is Fertilization?

A

The process by which one gamete combines with another gamete to form a diploid zygote.

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8
Q

What is a diploid cell?

A

A cell that contains paired chromosomes, one from each parent.

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9
Q

What are sex chromosomes?

A

One of the 23 pairs of chromosomes in a normal cell that determines an individual’s gender.

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10
Q

What are autosomes?

A

The 22 pairs of chromosomes in a normal cell that does not determine an individual’s gender.

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11
Q

What are the two types of sex chromosomes?

A

X and Y. Individuals with two X chromosomes are female. Individuals with X and Y are male.

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12
Q

What is meiosis?

A

A type of cell division that reduces the number of chromosomes and forms gametes.

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13
Q

What does meiosis do?

A

It halves the chromosome number through the separation of homologous chromosomes. A cell with 2n chromosomes will have gametes with n chromosomes after meiosis.

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14
Q

Where does meiosis occur?

A

Meiosis occurs in the reproductive structures of organisms that reproduce sexually.

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15
Q

What is crossing over?

A

A process during which chromosomal segments are exchanged between a pair of homologous chromosomes.

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16
Q

What happens to DNA in interphase 1 during meiosis?

A

Chromosomes replicate and chromatin condenses.

17
Q

What happens to DNA in prophase 1 during meiosis?

A

Homologous chromosomes pair and crossing over occurs.

The nuclear envelope breaks down and spindles form.

18
Q

What happens to DNA during metaphase 1 in meiosis?

A

Spindle apparatus attaches to centromeres. Homologous chromosomes line up at the equator.

19
Q

What happens to DNA during anaphase 1 in meiosis?

A

Homologous chromosomes separate and move to opposite poles of the cell.

20
Q

What happens to DNA during telophase 1 in meiosis?

A

Spindles break down, chromosomes uncoil to form two nuclei, and the cell divides.

21
Q

What happens to DNA during prophase 2 in meiosis?

A

Chromosomes condense. Spindles form in each new cell. Spindle fibers attach to chromosomes.

22
Q

What happens to DNA during metaphase 2 in meiosis?

A

Centromeres of chromosomes line up randomly at the equator of each cell.

23
Q

What happens to DNA during anaphase 2 in meiosis?

A

Centromeres split. Sister chromatids separate and move to opposite poles.

24
Q

What happens to DNA during telophase 2 in meiosis?

A

Four nuclei form around chromosomes. Spindles break down. Cells divide.

25
Q

What are the final Products of meiosis?

A

Four cells have formed. Each nucleus contains a haploid number of chromosomes.

26
Q

How does meiosis provide variation?

A

Depending on how chromosomes line up at the equator, four gametes with four different combinations of chromosomes can result.

27
Q

What happens to DNA during asexual preproduction?

A

During asexual reproduction, chromosome number is maintained by mitosis.
The organism inherits all of its chromosomes from a single parent.
The new individual is genetically identical to its parent.

28
Q

How do species reproduce in nature?

A

Bacteria reproduce asexually, whereas most protists reproduce both asexually and sexually.
Most plants and many of the more simple animals can reproduce both asexually and sexually.

29
Q

What are Telomeres?

A

They are chromosomes that end in protective caps that consist of DNA associated with proteins.
Telomeres might be involved in aging and cancer.

30
Q

What is a karyotype?

A

A karyotype is a type of micrograph in which the pairs of homologous chromosomes are arranged in decreasing size.

31
Q

What is nondisjunction and where does it occur?

A

Cell division during which sister chromatids fail to separate properly. Nondisjunction occurs in both autosomes and sex chromosomes.

32
Q

What results from nondisjunction?

A

Nondisjunction can result in extra copies of certain chromosomes or only one copy of a particular chromosome in offspring.
In humans, alterations of chromosome numbers are associated with serious disorders, which are often fatal.

33
Q

What causes down syndrome?

A

Down syndrome is the result of an extra chromosome 21 and is often called trisomy 21.

34
Q

What is Turner’s syndrome?

A

An individual with Turner’s syndrome has only one sex chromosome. The condition results from fertilization with a gamete that had no sex chromosome.

35
Q

What is Klinefelter’s syndrome?

A

An individual with Klinefelter’s syndrome has three sex chromosomes. This condition results from fertilization with a gamete that had two sex chromosomes.

36
Q

What does meiosis form in plants?

A

Spores.

Biology (13 decks)

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