Unit 4

Question 1

The ____________ is an orderly sequence of events that describes the stages of a cell’s life from the division of a single parent cell to the production of two new daughter cells. The mechanisms involved in the cell cycle are highly regulated.

Answer 1

Cell cycle

Question 2

A cell’s DNA, packaged as a double-stranded DNA molecule, is called its _____________

Answer 2

Genome

Question 3

In prokaryotes, the genome is composed of a _____________
-The region in the cell containing this genetic material is called a ____________

Answer 3

single, double-stranded DNA molecule in the form of a loop or circle
Nucleoid

Question 4

In eukaryotes, the genome consists of ___________

Answer 4

Several double-stranded linear DNA molecules

Question 5

Human body cells have _____ chromosomes, while human gametes (sperm or eggs) have ____ chromosomes each

Answer 5

46
23

Question 6

A typical body cell, or somatic cell, contains two matched sets of chromosomes, a configuration known as __________

Answer 6

Diploid

Question 7

The letter n is used to represent a single set of chromosomes; therefore, a diploid organism is designated ___________
-Human cells that contain one set of chromosomes are called gametes, or sex cells; these are eggs and sperm, and are designated _____________ or __________

Answer 7

2n
1n
Haploid

Question 8

Matched pairs of chromosomes in a diploid organism are called _______________

Answer 8

Homologous chromosomes

Question 9

Homologous chromosomes are the same length and have specific nucleotide segments called ____________ in exactly the same location, or _______

Answer 9

Genes
Locus

Question 10

___________, the functional units of chromosomes, determine specific characteristics by coding for specific proteins.
-___________ are the variations of those characteristics

Answer 10

Genes
Traits

Question 11

During _____________, the cell grows and DNA is replicated

Answer 11

Interphase

Question 12

During the _____________, the replicated DNA and cytoplasmic contents are separated, and the cell divides.

Answer 12

Mitotic phase

Question 13

DNA replicates in the ____________ of interphase

Answer 13

S phase

Question 14

After replication, the chromosomes are composed of two linked sister _____________. When fully compact, the pairs of identically packed chromosomes are bound to each other by cohesion proteins. The connection between the sister chromatids is closest in a region called the ______________

Answer 14

Chromatids
Centromere

Question 15

The first stage of interphase is called the ___________ because, from a microscopic aspect, little change is visible
-The cell is accumulating the building blocks of chromosomal DNA and the associated proteins as well as accumulating sufficient energy reserves to complete the task of replicating each chromosome in the nucleus

Answer 15

G1 Phase (first gap)

Question 16

In the ____________, DNA replication can proceed through the mechanisms that result in the formation of identical pairs of DNA molecules—sister chromatids—that are firmly attached to the centromeric region

Answer 16

S Phase

Question 17

The centrosome is duplicated during the ____________

Answer 17

S phase

Question 18

The two centrosomes will give rise to the ____________, the apparatus that orchestrates the movement of chromosomes during mitosis.

Answer 18

Mitotic spindle

Question 19

At the center of each animal cell, the centrosomes of animal cells are associated with a pair of rod-like objects, the __________, which are at right angles to each other
-They help organize cell division
-Are not present in the centrosomes of other eukaryotic species, such as plants and most fungi

Answer 19

Centrioles

Question 20

In the ___________, the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation
-Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic phase.
-There may be additional cell growth during this time

Answer 20

G2 phase (second gap)

Question 21

The ______________ is a multistep process during which the duplicated chromosomes are aligned, separated, and move into two new, identical daughter cells

Answer 21

Mitotic phase (M phase)

Question 22

2 parts of M phase

Answer 22

Mitosis
Cytokinesis

Question 23

Parts of mitosis

Answer 23

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 24

What happens during Prophase

Answer 24

Centrosomes begin to move to opposite sides
-DNA condenses

Question 25

What happens during Prometaphase

Answer 25

Nuclear membrane dissolves -Centrosomes connect with chromosomes

Question 26

What happens during Metaphase

Answer 26

Chromosomes line up in center of cell (metaphase plate)

Question 27

What happens during Anaphase

Answer 27

Cohesion degrades -Daughter chromosomes segregate

Question 28

What happens during telophase

Answer 28

Microtubules disconnect -Nuclei reform

Question 29

Mitosis creates ______________ daughter cells

Answer 29

Genetically identical

Question 30

In prometaphase, each sister chromatid develops a protein structure called a ___________ in the centromeric region -The proteins of this attract and bind mitotic spindle microtubules

Answer 30

Kinetochore

Question 31

What happens in cytokinesis

Answer 31

Animal cells divide by "pinching in" of plasma membrane -Actin microfilaments and myosin form ring under plasma membrane -Contract to produce the pinching, forming cleavage furrow

Question 32

Centrosomes are _________________________. They recruit tubulin and trigger the formation of microtubules into spindles

Answer 32

Microtubule organization center

Question 33

The production of progeny from a single parent is called ________________. The genetic content of each progeny is genetically identical to the parent, and are technically _______________

Answer 33

Asexual reproduction Clones

Question 34

The cells produced by mitosis are produced ____________ -Variation of these cells is only due to ____________ or ______________

Answer 34

Asexually Random mutations or environmental effects

Question 35

Other forms of asexual reproduction include __________ (yeast, hydra) and ____________ (bacteria)

Answer 35

Budding Binary fission

Question 36

____________ combines the genetic material from 2 different organisms to create a genetically unique third organism

Answer 36

Sexual reproduction

Question 37

Gametes fuse to produce a single cell, the __________

Answer 37

Zygote (fertilized egg)

Question 38

Offspring are _____________ even before mutations

Answer 38

Genetically varied

Question 39

Each parent contributes a complete set of chromosomes in a sex cell or ___________

Answer 39

Gamete

Question 40

Sexual reproduction requires ____________, the union of two cells from two individual organisms

Answer 40

Fertilization

Question 41

__________ consists of two nuclear divisions that reduce the diploid chromosomes number to haploid

Answer 41

Meiosis

Question 42

In meiosis, DNA is replicated ________

Answer 42

Once

Question 43

Meiosis occurs only in the ___________, a population of stem cells that reside in the gonads

Answer 43

Germ cells

Question 44

During prophase 1, the homologous chromosomes pair, which is called _____________

Answer 44

Synapsis

Question 45

Prophase 1: a protein scaffold- the ________________- joins the homologous chromosomes. It is composed of proteins similar to the cohesions that hold sister chromosomes together

Answer 45

Synaptonemal complex

Question 46

The synaptonemal complex supports the exchange of chromosomal segments between non-sister homologous chromatids, a process called _________________

Answer 46

Crossing over

Question 47

Prophase 1: Crossing over can be observed visually after the exchange as __________

Answer 47

chiasmata (singular = chiasma)

Question 48

Located at intervals along the synaptonemal complex are large protein assemblies called ________________. These assemblies mark the points of later chiasmata and mediate the multistep process of crossover—or genetic recombination—between the non-sister chromatids

Answer 48

Recombination nodules

Question 49

At the end of prophase I, the pairs are held together only at the chiasmata and are called ___________ because the four sister chromatids of each pair of homologous chromosomes are now visible.

Answer 49

Tetrads

Question 50

What happens during prophase 1

Answer 50

Chromosomes condense, and the nuclear envelope fragments. Homologous chromosomes bind firmly together along their length, forming a tetrad. Chiasmata form between non-sister chromatids. Crossing over occurs at the chiasmata. Spindle fibers emerge from the centrosomes

Question 51

What happens during Prometaphase 1

Answer 51

Homologous chromosomes are attached to spindle microtubules at the fused kinetochore shared by the sister chromatids. Chromosomes continue to condense and the nuclear envelope completely disappear

Question 52

What happens during Metaphase 1

Answer 52

Homologous chromosomes randomly assemble at the metaphase plate, where they have been maneuvered into place by the microtubules

Question 53

What happens during Anaphase 1

Answer 53

Spindle microtubules pull the homologous chromosomes apart. The sister chromatids are still attached at the centromere

Question 54

What happens in telophase 1 and cytokinesis

Answer 54

Sister chromatids arrive at the poles of the cell and begin to decondense. A nuclear envelope forms around each nucleus and the cytoplasm is divided by a cleavage furrow. The result is two haploid cells. Each cell contains one duplicated copy of each homologous chromosome pair

Question 55

What happens in prophase 2

Answer 55

Sister chromatids condense. A new spindle begins to form. The nuclear envelope starts to fragment

Question 56

What happens in prometaphase 2

Answer 56

The nuclear envelope disappears, and the spindle fibers engage the individual kinetochores on the sister chromatids

Question 57

What happens in metaphase 2

Answer 57

Sister chromatids line up at the metaphase plate

Question 58

What happens in Anaphase 2

Answer 58

Sister chromatids are pulled apart by the shortening of the kinetochore microtubules. Non-kinetochore microtubules lengthen the cell

Question 59

What happens in Telophase 2 and cytokinesis

Answer 59

Chromosomes arrive at the poles of the cell and decondense. Nuclear envelopes surround the four nuclei. Cleavage furrows divide the two cells into four haploid cells

Question 60

Meiosis: Anaphase 1

Answer 60

Homologous chromosomes separate to opposite poles -Daughter nuclei contain only one set of chromosomes, each consisting of 2 chromatids

Question 61

Functions of meiosis

Answer 61

Reduce chromosome number from diploid to haploid -Ensure each gamete gets a complete set of chromosomes -Promotes genetic diversity of products -8.3 million different possibilities

Question 62

Meiosis: Prometaphase 1

Answer 62

Nuclear envelope and nucleoli disappear -Spindle forms; kinetochores of both chromatids of a chromosome attach to the same half-spindle

Question 63

Meiosis: Metaphase 1

Answer 63

Homologous chromosomes move to equatorial plate -The specific arrangement of homologous chromosome pairs is determined randomly and independently from the other pairs -Allows mixing of parental chromosomes in final gametes

Question 64

How many sperm and ovum are produced in Meiosis

Answer 64

Sperm=4 Ovum=1

Question 65

Genetic variation in asexual reproduction

Answer 65

Mutation

Question 66

Genetic variation in sexual reproduction

Answer 66

Crossing over -Independent assortment of chromosomes -Randomness of fertilization -Mutation

Question 67

What is nondisjunction

Answer 67

-Occurs when homologous chromosomes or sister chromatids fail to separate -Either result in aneuploidy

Question 68

Aneuploidy

Answer 68

-Creates trisomies or monosomies -Most embryos from these zygotes do no survive -Trisomy 21= Down Syndrome -Monosomy X= Turner Syndrome -XXY= Klinefelter Syndrome

Question 69

____________ are highly condensed, tightly wrapped linear molecules of DNA. Depending on the length of the molecule, each DNA molecule contains hundreds to thousands of genes, the genetic information to encode hundreds to thousands of proteins

Answer 69

Chromosomes

Question 70

Each chromosome contains a specific set of __________, in a __________ order

Answer 70

Genes Specific

Question 71

Gene variants that arise by mutation and exist at the same relative locations on homologous chromosomes are called ___________

Answer 71

Alleles

Question 72

An organism’s underlying genetic makeup, consisting of both physically visible and non-expressed alleles, is called its _________

Answer 72

Genotype

Question 73

The observable traits expressed by an organism are referred to as its ____________

Answer 73

Phenotype

Question 74

Every diploid cell/organism has two alleles of each gene. If they contain two of the same alleles, they are called _________. If they have two different alleles, they are called ____________

Answer 74

Homozygous Heterozygous

Question 75

Every haploid cell has a single allele of each gene. The specific combination of alleles in a cell denotes its ____________

Answer 75

Genotype

Question 76

Two alleles for a gene segregate during gamete formation, and are rejoined at random, one from each parent, during fertilization

Answer 76

Law of segregation

Question 77

Proteins are the bulk of your solid matter. There are likely over 100,000 different proteins in your body, each with a specific structure and function. These observable or measurable traits are called the ____________

Answer 77

Phenotype

Question 78

_____________ occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygous genotypes

Answer 78

Incomplete Dominance ('blended phenotype) - Also called partial, semi-dominance, or intermediate inheritance)

Question 79

Example of Incomplete dominance

Answer 79

Snapdragon flower color, eggplant color -Heterozygotes show an intermediate or blended phenotype

Question 80

_____________ occurs when the contributions of both alleles are visible in the phenotype. Two different alleles for a gene are phenotypically expressed in heterozygotes

Answer 80

Codominance

Question 81

Example of codominance

Answer 81

Human ABO blood group system

Question 82

_________ are traits determined by more than one gene

Answer 82

Polygenic

Question 83

Human skin color is also characterized as a ____________. These genetic traits are influenced by the enviroment

Answer 83

Multifactorial trait

Question 84

Genetics use _________ to determine how traits or conditions are transmitted in families

Answer 84

Pedigrees

Question 85

A pedigree analysis of the recessive allele for phenylketonuria shows that:

Answer 85

Development of condition requires the inheritance or two recessive alleles -Condition can skip generations -Heterozygotes are termed carriers -Phenotype occurs equally in both sexes

Question 86

Autosomal recessive diseases are observed more frequently in _____________ relationships (Relationships in which the couple is related by blood, such as first cousins) because the individuals are descendants of the same ancestors and are, therefore, more likely to carry the same alleles

Answer 86

Consanguineous

Question 87

A pedigree analysis of the dominant allele for Huntington's disease shows that:

Answer 87

Having one dominant allele is sufficient for condition development -Every affected person has at least one affected parent -50% of offspring of just one affected parent are also likely to be affected -Phenotype occurs equally in both sexes

Question 88

Pedigrees of X-linked recessive traits:

Answer 88

Phenotype appears much more often in males -Male can pass allele only to his daughters -Daughter who receive one mutant X are heterozygous carriers -Phenotype can skip generation if mutation is passed from male to his daughter and then to her son

Question 89

Pedigrees of X-linked dominant traits:

Answer 89

Only one copy of a disease allele on the X chromosome is requires for an individual to be susceptible to an X-linked dominant disease -Both males and females can be affected, although males may be more severely affected because they only carry one copy of genes found on the X chromosome -When a female is affected, each pregnancy will have a 50% chance for the offspring to inherit the disease allele -When a male is affected, all his daughters will be affected, but none of his sons will be affected