Chapter 9, sexual reproduction and meiosis

in asexual reproduction one parent organism replicates its DNA and splits the contents of one cell into how many cells?

two identical daughter cells.

asexual reproduction is rare or common?

it is rare, single cell organisms like bacteria, archaea, and protists do it all the time, but among multicellular organisms like humans its not common

in sexual reproduction the DNA of the offspring comes from two parents ___ fuses with the ___ yielding the first cell of the next generation.

This results in:

sperm, egg

genetically diverse offspring

attracting a mate a nd producing sex cells requires a lot of energy which is costly to the organism… so why is sexual reproduction so common?

The benefits of sexual reproduction include increased genetic diversity, which enhances adaptability and survival of offspring in changing environments.

which two organisms are genetically the most similar?

a dog and its puppy or two ameobas

the ameobas

how many sets of chromosomes does a diploid cell have?

A diploid cell has two sets of chromosomes, one set inherited from each parent, 

most cells in a sexually reproducing organism have two sets of chromosomes: one from mum and one from papa

cells with two sets of chromosomes are called?

diploid cells

human cells contain __ homologous sets of chromosomes?

23

the image to the right is called a __ it shows all of the chromosomes from a diploid human  cell

karyotype

22 out of the 23 chromosomes in humans are known as?

autosomes, which are the chromosomes that are the same in both males and females

each autosome pair consists of ___ equally sized chromosomes

two

human cells contain one set of?

sex chromosomes two XX is a female and a XY is a male

homologous sets of chromosomes carry the same sets of?

genes, although they may have different alleles.

the chromosomes of a ___ are similar in size and structer

homologous pair

the dna sequence is not exactly the same in a homologous set but?

each chromosome in a homologus pair has genes for the same traits

homologous sets of chromosomes are not identical true or false

True

alleles are alternative versions of the same?

gene

after replication, each chromosome consists of?

identical sister chromatids

when members of a homologous pair are replicated identical alleles are on?

sister chromatids

does DNA replication change chromosom e number or make cells diploid?

DNA replication does not change chromosome number; it simply duplicates the genetic material, resulting in two identical sister chromatids for each chromosome.

the image below shows two chromosomes from once cell which statement is true

a. both came from the persons mother?

b. 1-2 pair is identical to the 3-4 pair

c. 1 is identical to 2

d. the chromosomes have not been replicated yet

_{C 1 is identical to 2}

what is shown in a karotype use these terms in your answer

sex chromosome 

homologous

autosome

allele

diploid

gene

A karyotype is a visual representation of an individual's chromosomes, showcasing the number and structure of homologous pairs, including sex chromosomes and autosomes. It provides insights into the diploid number and allele variations for specific genes.

gametes like the sperm anf egg cell are?

haploid sex cells, meaning they only have one set of chromosomes

when gametes fuses it creates

a zygote, the first cell of an organism

it grows and devolops by mitosis

in adults specialized diploid cells called ___ divide by meiosis to form haploid gametes

germ cells

Meiosis halves the chromosome number and scrambles the allels how many gametes are produced?

Four unique gametes are produced.

compare the chromosomes you would find in a mans germ cells, sperm cells, and the rest of his body cells

Germ cells contain diploid chromosomes, sperm cells are haploid with half the number of chromosomes, while body cells are also diploid.

in meiosis dna replicates once but the nucleus divides?

nucleus divides twice

meiosis reduces the number of chromosomes by half, the germ cells start out with two pairs of homologous chromosomes then it turns into?

gametes that have two single unpaired chromosomes per cell

meiosis interphase

DNA replicates cell produces protiens needed for cell divison

meiosis prophase I early

chromosomes condense and become visible

prophase I late meiosis

crossing over occurs, spindles form, nuclear envelope breaks up

metaphase I

paired homologous chromosomes line up along equator of cell

anaphase I

homologous chromosomes seperate to opposite sides of the cell, sister chromatids remain joined

telophase and cytokensis

nuclear envelops form aroujnd chromosomes which may temprarily decondense, sindle diseapres then cells divide into two

Meiosis II prophase

spindles form nuclear envelope breaks up

metaphase II 

chromosomes line up along equator of the cella

anaphase II

homologous chromosomes separate and move to opposite poles.

telaphase II and cytokensis

the nuclear envelope reforms around each set of chromosomes, followed by the division of the cytoplasm into two distinct cells.

product of meiosis II

four genetically diverse haploid cells

a zygote contains 40 chromosomes how many chromosomes are in a ferrets sperm cell?

20 chromosomes

how does meiosis reduce the number of chromosomes by half

Meiosis involves two rounds of division, meiosis I and meiosis II, which separate homologous chromosomes and sister chromatids, respectively, resulting in cells with half the original chromosome number.

meiosis generates genetic variability how?

the chromosomes in the gamets produce meisosis are different because of prophase I which is crossing over and independent assortment in meta phase II

ccrossing over occurs in meiosis prophase I what is it?

during crossing over two homologous chromosomes pair up an exchange pieces scrambling the genetic material

ubdpendent assortment occurs in meiosis mentaphase I, what is it?

in indpenden assortment chromosome pairs align randomly scrambling the combination of chromosomes for each gamete

independent assortment produces many chromosome combinations a germ cell with three pairs of chromosomes has ____ possible arrangements during metaphase, yielding prossible gamets'

2³ =8

4

sometimes an embryo splits into two, then it develops independently which makes

two genetically identical siblings, known as identical twins.

dizygotic twins have uique DNA

fraternal tiwns are a testament to the varition amoung gametes two sperm cells fertilize two seperate egg cells and the offspring might look very different

many sets of triplets consists of a pair and a spare, that is two identical babies and one non identical baby producing this arrangements requires how many sperms anf eggs

2,2

each human germ cell contains 23 sets of homologous chromosomes

calculate the number of possible chromosome combinations for the gametes

These chromosomes are organized into 23 pairs, with one chromosome from each parent, making a total of 46 chromosomes per diploid somatic cell.

how are mitosis and meiosis different in division

Mitosis results in two identical diploid daughter cells, whereas meiosis produces four genetically diverse haploid gametes through two rounds of division.

compare and contrast meiosis and mitosis in terms of

which cells carry them out

the events that occur

number and type of new cells produced

chromosomes in the new cels haploid vs diploid

the processes of chromosome division and genetic variation. Mitosis results in identical diploid cells, while meiosis leads to genetically diverse haploid gametes.

if chromosomes fail to seperate properly abnormal gametes form this failure to seperate is called?

nondisjunction.

in what phase does nondisjunction occur?

Nondisjunction can occur during either anaphase I of meiosis or anaphase II of meiosis, leading to the failure of homologous chromosomes or sister chromatids to separate.

down syndrome is caused by?

nondisjunction of chromosome 21, resulting in an extra copy of the chromosome. they have three rather than two

nondisjunction of sex chromosomes cause?

sex disorders

spermatogensis produces?

four sperm cells for each germ cell

oogenesis produces one egg for?

each germ cell, ensuring proper development and maturation.

compare gamete devlopment in males females and spore producing plants

In male and female animals, gamete development involves meiosis to produce sperm and eggs, respectively, while in spore-producing plants, sporophytes undergo meiosis to form spores, which develop into gametophytes.

how many sets of chromosomes do haploid cells vs diploid cells have?

Haploid cells have one set of chromosomes, while diploid cells have two sets.

sperm and egg have one chromosome each, they come together to create a zygote which has?

two sets of chromosomes, restoring the diploid state. then it goes through mitosis and its sets of chromosomes never changes

homologous chromosomes have similar?

size, shape, and GENE LOCATION

sister chromatids vs homologous chromosomes

Sister chromatids are identical copies of a chromosome that are connected by a centromere, while homologous chromosomes are pairs of chromosomes, one inherited from each parent, that have the same genes but may have different alleles.

gern cells produce?

gametes, which are sperm and egg cells.

meiosis ___ the chromosomes and ___ alleles

halves, scrambles

produces 4 genetically unique daughter cells

dna replicates once but the nucleus divides twice

in meiosis, DNA replicates ___ but the nucleus divides___

once, twice

crossing over is specific to?

prophase I in meiosis, it does not happen in mitosis.

prophase I four main things happening:

spindles form from the centrosomes, nuclear envelope condence, nuclear envelope breaks up, DNA condenses.

when does crossing over happen?

It occurs during prophase I of meiosis, allowing for genetic recombination between homologous chromosomes.

what is the main difference between meiosis I and II

Meiosis I reduces chromosome number by half, while meiosis II separates sister chromatids without further reducing chromosome number.

Meiosis I involves homologous chromosomes, whereas Meiosis II involves sister chromatids.

homologous pair of chromosomes vs sister chromatids

A homologous pair of chromosomes consists of one chromosome from each parent that are similar in shape, size, and gene content, while sister chromatids are identical copies of a single chromosome connected at the centromere, formed during DNA replication.

why does crossing over not occur in prophase I

Crossing over does occur in prophase I; it is a crucial process for genetic diversity. However, it does not occur in prophase II of meiosis.

when does independent assortment occur?

Independent assortment occurs during meiosis I, specifically in metaphase I, when homologous chromosomes line up at the cell's equatorial plane.

name everything different about mitosis and meiosis

Mitosis produces two identical diploid cells, while meiosis produces four genetically diverse haploid cells. Mitosis involves one division, while meiosis has two divisions (meiosis I and meiosis II). Additionally, meiosis includes processes like crossing over and independent assortment that increase genetic variation.

non-disjunction happens in what phase that goes wrong

anaphase I or II