Chapter 10 - Cell Reproduction and Meiosis

Question 1

Genome

Answer 1

a cell DNA, packaged as a double-stranded DNA molecule

Question 2

Genome - Prokaryote

Answer 2

in prokaryotes, the genome is composed of a single double-stranded DNA molecule in the form of a loop or circle
-plasmids = smaller loops of DNA, not essential for normal growth but allow the exchange of beneficial new genes such as antibiotic resistance

Question 3

Genome - Eukaryote

Answer 3

in eukaryotes, the genome consists of several, double-stranded linear DNA molecules
-a typical body cell (somatic) contains 2 matched or homologous sets of chromosomes
-human cells that contain one set of chromosomes are called gametes and are designed as haploid
-sex cells form in reproductive organs, 2 types: sperm and egg

Question 4

Sexual Reproduction

Answer 4

Fertilization: occurs when an egg cell and sperm cell join together; a new cell is formed
-the new cell that forms from fertilization = zygote
-after fertilization, the zygote goes through mitosis and cell division
-mitosis and cell division produce nearly all cells in a multicellular organism
-23 pairs of homologous chromosomes in a female human somatic cell

Question 5

Chromosomes and Alleles

Answer 5

-a variation of individuals within a species is due to the specific combination of the genes inherited from both parents
-even a slightly altered sequence of nucleotides within a gene can result in an alternate trait (blood type)

Question 6

Blood Type

Answer 6

-humans have 4 blood types (A, B, AB, O)
-A and B are codominant to each other
-O is recessive to A and B

Question 7

Diploid vs Haploid Cell

Answer 7

-in humans, each somatic cell has 46 chromosomes (23 mom and 23 dad) or 23 homologous chromosomes (homologs)
-Haploid Cells - somatic cells, have one set of chromosomes, n
-Diploid Cells - gametes, have 2 sets of chromosomes, 2n
-pairs of chromosomes that have genes for the same traits in the same order (locus) are called homologous chromosomes because one chromosome is inherited from each parent so chromosomes are not always identical.

Question 8

Ophioglossum reticulatum

Answer 8

species with the most chromosomes (1260)
-chromosome number is very important

Question 9

Fusion vs Polyploidy

Answer 9

-chromosome number can change over time
-Fusion: they can stick together by accident; decreases the number of chromosomes but little/no genetic information is lost
-Polyploidy: extra chromosomes can happen through mistakes when cells divide; increases the number of chromosomes
-BOTH happen by chance

Question 10

Chromosome # Importance

Answer 10

-important to have the correct # of chromosomes
-if a zygote has too many or too few chromosomes, it will not develop properly
-the process of meiosis helps maintain the correct number of chromosomes
-if a mistake occurs in animal cells (sometimes the zygote dies, if the zygote lives, every cell in that organism will have the wrong amount of chromosomes and may not grow normally)

Question 11

Haploid Cells

Answer 11

organisms that reproduce sexually also form egg and sperm cells (sex cells)-sex cells have one chromosome from each pair of chromosomes
-cells that have only 1 chromosome in each pair
-organisms that produce sex cells using a special type of cell division (meiosis)

Question 12

Meiosis

Answer 12

-one diploid cell divides and makes 4 haploid sex cells
-occurs only during the formation of sex cells
-meiosis involved 2 divisions of the nucleus and cytoplasm
-results in 4 haploid cells, each with half the # of chromosomes as the original cell

Question 13

Phases of Meiosis

Answer 13

-reproductive cell goes through interphase before beginning meiosis I
-during interphase, the reproductive cell grows and copies, or duplicates its chromosomes
-each duplicated chromosome consists of 2 sister chromatids joined by a centromere

Question 14

Cell Cycle

Answer 14

4 phases of cell cycle of replication
-G1, S, G2, M
-interphase: G1, S, G2, M; mitotic phase

Question 15

G1 Phase

Answer 15

-the cell is quite active at biochemical level
-accumulate building blocks of chromosomal DNA and associated protein

Question 16

S Phase

Answer 16

synthesis of DNA

Question 17

G2 Phase

Answer 17

-the cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation

Question 18

Mitotic Phase

Answer 18

-a multistep process during which duplicated chromosomes are aligned, separated, and moved to opposite poles of the cell, and then the cell is divided into 2 new identical slaughter cells
-DNA replication occurs during “S” Phase

Question 19

Meiosis 1 –> Prophase 1

Answer 19

-duplicated chromosomes condense, or shorten, and thicken
-homologous chromosomes come together and form pairs
-membrane around the nucleus break apart and nucleolus disappears

Question 20

Meiosis 1 –> Metaphase 1

Answer 20

-homologous chromosome pairs line up along the middle of the cell
-spindle fiber attaches to each chromosome

Question 21

Meiosis 1 –> Anaphase 1

Answer 21

-chromosome pairs separate and are pulled towards opposite ends of the cell
-sister chromatids stay together

Question 22

Meiosis 1 –> Telephase 1

Answer 22

-membrane forms around each group of duplicated chromosomes
-cytoplasm divided through cytokinesis and 2 daughter cells form
-sister chromatids remain together
-after meiosis 1, 2 cells formed go through second division of nucleus and cytoplasm

Question 23

Meiosis 2 –> Prophase 2

Answer 23

-chromosomes NOT copied again before prophase II
-they remain short and thick sister chromatids
-membrane around the nucleus breaks apart and the nucleus disappears in each cell

Question 24

Meiosis 2 –> Metaphase 2

Answer 24

-pairs of sister chromatids line up along middle of cell single file

Question 25

Meiosis 2 –> Anaphase 2

Answer 25

-sister chromatids of each duplicated chromosome pulled apart then move toward opposite ends of cells

Question 26

Meiosis 2 –> Telophase 2

Answer 26

-the final phase of meiosis
-nuclear membrane forms around each set of chromatids
-cytoplasm divides through cytokinesis and 4 haploid cells form

Question 27

Crossing Over

Answer 27

-exchange of DNA segments produces new combos of alleles among offspring = genetic recombination
-the main difference between recombination and crossing over is that recombination is the production of different combinations of alleles in offspring while crossing over ONLY happens at the very beginning of meiosis, during prophase 1

Question 28

Meiosis Importance

Answer 28

-important to sexual reproduction
-forms the correct haploid number of chromosomes in organisms when sex cells join
-meiosis also leads to genetic variation
-helps maintain diploid cells in offspring by making haploid sex cells
-when haploid cells join together during fertilization, diploid zygote of fertilized egg forms
-zygote divided by mitosis and cell division and creates diploid organism

Question 29

Advantages of Sexual Reproduction

Answer 29

-offspring inherit 1/2 of their DNA from each parent
-inheriting different DNA means each offspring has a different set of traits
-some may have traits to survive harsh conditions
-some traits may help organisms keep from getting infected with disease
-selective breeding: breeding with certain individuals because of the traits they have; used to produce many types of plants/animals