Chapter 13 Flashcards Preview

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Flashcards in Chapter 13 Deck (63):
1

gentics

the scientific study of heredity and variation

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heredity

The transmission of traits from one generation to the next

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variation

demonstrated by the differences in appearance that offspring show from parents and siblings

4

true or false: it is genes that are actually inheritied

TRUE

5

genes

units of heredity, are made up of segments of DNA

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how are genes passed on to the next generation?

via reproductive cells called gametes

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locus

the specific location a gene has on a certain chromosome

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DNA is packaged into...

a chromosome

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asexual reproduction

a single individual passes genes to its offspring without the fusion of gametes

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clone

a group of genetically identical individuals from the same parent

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sexual reproduction

two parents give rise to offspring that have unique combinations of genes inherited from the two parents

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life cycle

the generation to generation sequence of stages in the reproductive history of an organism

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somatic cells have how many pairs of chromosomes?

23 pairs

14

karyotype

an ordered display of the pairs of chromosomes from a cell

15

homologous chromosomes

two chromosomes in each pair
-same length, shape, and carry genes controlling the same inherited characters

16

sex chromosomes

determine the sex of an individual, called x and y
-females have pair of x chromosome
-males have one x chromosome and one y chromosome

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the remaing 22 pairs of chromosomes apart from the sex chromosomes are called

autosomes

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each pair of homologous chromosomes include...

one chromosome from each parent

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the 46 chromosomes in a human somatic cell are two sets of 23; one from _____ and one from _____

mother
father

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diploid cell

has two sets of chromosomes
for humans the diploid number is 46

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haploid cell

this is a gamete that contains a single set of chromosomes
-from humans, the haploid number is 23
--22 autosomes and 1 sex chromosome

22

an unfertilized egg always has the chromosome..

x

23

true or false;
a sperm cell, may have either x or y chromosome

true

24

fertilization

the union of gametes (sperm and egg)

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zygote

fertilized egg
-has one set of chromosome from each parent
-zygote produces somatic cells by mitosis and develops into an adult

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when do people start to produce haploid gametes?

at sexual maturity

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meiosis

results in one set of chromosome in each gamete

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alternation of generations (by plants and some algae)

-includes both a diploid and a haploid multicellular stage
-the diploid organism, called the sporophyte, makes haploid spores by meiosis
-ea. spore grows by mitosis into a haploid organism called a gametophyte
-a gametophyte makes haploid gametes by mitosis
-fertilization of gametes result in a diploid sporophyte

29

alternation of generations (by fungi and protists)

• In most fungi and some protists, the only diploid stage is the single-celled zygote; there is no multicellular diploid stage
• The zygote produces haploid cells by meiosis
• Each haploid cell grows by mitosis into a haploid multicellular organism
• The haploid adult produces gametes by mitosis

30

true or false: only diploid cells can divide by mitosis

FALSE
depending on the type of life cycle, either haploid or diploid cells can divide by mitosis

31

true or false: only diploid cells can undergo meiosis

true

32

meiosis takes place in two sets of cell divisions....

1. Meiosis 1
2. Meiosis 2

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the two cell divisions result in ___ daughter cells
and each daughter cell has _______

-four
-only half as many chromosomes as the parent cell

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what happens in Meioisis 1:

(reductional division): homologous chromosomes pair up and separate, resulting in two haploid daughter cells with replicated chromosomes

35

what happens in Meiosis 2:

(equational division) sister chromatids separate
---the result is four haploid daughter cells with unreplicated chromosomes

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what happens in the interphase of meiosis?

-pair of homologous chromosomes in diploid parent are duplicated
-starts as / / and now is // //
-two pairs of sister chromatids

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what are the four phases of meiosis 1

prophase 1
metaphase 1
anaphase 1
telophase 1 and cytokinesis

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what happens in prophase 1 of meiosis?

-crossing over and synapsis
-homologous chromosomes loosley pair up, aligned gene by gene

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synapsis

homologous chromosomes loosely pair up, aligned gene by gene

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crossing over

-nonsister chromatids exchange DNA segments
-each pair of chromosomes form a tetrad, a group of four chromatids

41

chismata

x shaped regions where crossing over occured

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what happens in Metaphase 1 of meiosis 1

-tetrads line up at the metaphase plate, with one chromosome facing each pole
-microtubules from one pole are attached to the kinetochore of one chromosome at each tetrad
-microtubules from the other pole do the same

43

what happens in anaphase 1 of meiosis 1

-pair of homologous chromosomes separate
-one chromosome moves toward each pole, guided by the spindle aparatus
-sister chromatids remain attached at the centormere and move as one unit toward the pole

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what happens in telophase 1 and cytokinesis

- each half of the cell has a haploid set of chromosomes; each chromosome still consists of two sister chromatids
-cytokinesis happens simultaneously
-no chromosome replication occurs between the end of meiosis 1 and the beginning of meiosis 2 because the chromosomes are already duplicated

45

what are the four phases of meiosis 2

-prophase 2
-metaphase 2
-anaphase 2
-telophase 2 and cytokinesis

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what happens in prophase 2

-a spindle apparatus forms
-chromosomes move toward metaphase plate

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what happens in metaphase 2

-sister chromatids are arranged at the metaphase plate
-The kinetochores of sister chromatids attach to microtubules extending from opposite poles

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because of crossing over in meiosis 1 the two sister chromatids of each chromosomes are ....

no longer genetically identical

49

what happens in anaphase 2

-sister chromatds separate
-The sister chromatids of each chromosome now move as two newly individual chromosomes toward opposite poles

50

what happens in telophase 2

-the chromosomes arrive at opposite poles
-nuclei form, and chromosomes begin decondensing

51

what do you have at the end of meiosis 2

-four daughter cells, each with a haploid set of unreplicated chromosomes
-each daughter cell is genetically distinct from the others and from the parent cell

52

where does DNA replication occur in mitosis versus meiosis

both occur in interphase

53

number of divisions in mitosis versus meiosis

one in mitosis
two in meiosis

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when does synapsis of homologous chromosomes occur in mitosis versus meiosis

does not occur in mitosis
-Occurs during prophase I along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion

55

number of daughter cells and genetic composition in mitosis versus meiosis

two daughter cells in mitosis and genetically identical to the parent cell
-in meiosis it is four,ach haploid (n), containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other

56

what is the role in the animal body of the final product of mitosis versus meiosis

-in mitosis it enables multicellular adult to arise from zygote; produces cells for growth, repair, and, in some species, asexual reproduction
-in meiosis it produces gametes; reduces number of chromosomes by half and introduces genetic variability among the gametes

57

what are three events that are unique to meiosis (and all three occur in meiosis 1)

– Synapsis and crossing over in prophase I:
Homologous chromosomes physically connect and exchange genetic information
– At the metaphase plate, there are paired homologous chromosomes (tetrads), instead of individual replicated chromosomes
– At anaphase I, it is homologous chromosomes, instead of sister chromatids, that separate

58

what allows sister chromatids of a single chromosome stay together meiosis 1

-sister chromatid cohesion
--protein complexes called cohesins are responsible for this cohesion

59

when is the sister chromatid cohesion split? (mitosis versus meiosis)

In mitosis, cohesins are split at the end of metaphase
• In meiosis, cohesins are split along the chromosome arms in anaphase I (separation of homologs) and at the centromeres in anaphase II (separation of sister chromatids)

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alleles

mutations (changes in an organism's DNA) create different versions of genes which are alleles
-shuffling of alleles during sexual reproduction produces genetic variation

61

what three things contribute to genetic variation?

-independent assortment of chromosomes
-crossing over
-random fertilization

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homologous pairs of chromosomes orient randomly at ______ of meiosis

metaphase 1

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when does crossing over occur?

begins very early in prophase 1, as homologous chromosomes pair up gene by gene