Bio Formative 3/17/23
Haploid (n) - think Half
These cells have only one copy of each chromosome - gametes - (don't have homologous chromosomes)
Diploid (2n)
These cells have two copies of each chromosome - somatic cells - (have homologous chromosomes)
Homologous Chromomes
Two chromosomes with the same genes, but may have different versions of a gene (alleles) - one is from mother - one is from father
Mitosis vs. Meiosis
Type of Reproduction: Mit. - asexual Mei. - sexual
Fertilization
Uniting of a sperm (n) and an egg (n) cell n + n = 2n Results in a diploid zygote = fertilized egg
The sperm cell secretes a special ——— to penetrate the egg's cell membrane
enzyme
Life begins with the mating of a —— and ———
male and female
What is independent assortment?
- homologous pairs line up opposite each other at the equator of the cell - it's random which side of the equator the paternal and maternal chromosomes lie - theses pairs are separated, so one of each homologous pair ends up in the daughter cell - this creates a large number of possible combinations of chromosomes in the daughter cells produced
Prophase II (see picture in notes)
- nuclear membrane breaks down - centrosomes move to opposite sides of the cell - spindle fibers assemble
Prophase 1 (see picture in notes)
- nuclear membrane breaks down - centrosomes move to opposite sides of the cell - spindle fibers start to assemble - duplicated chromosomes condense - homologous chromosomes pair up
Telophase 1 (see picture in notes)
- nuclear membrane forms again (in some species) - spindle fibers disassemble - cell undergoes cytokinesis
Telophase II (see picture in notes)
- nuclear membranes from around chromosomes - spindle fibers break apart - cell undergoes cytokinesis
Anaphase 1 (see picture in notes)
- paired homologous chromosomes separate from each other and move to opposite sides of the cell - sister chromatids remain together
Anaphase II (see picture in notes)
- sister chromatids are pulled apart from each other - they move to opposite sides of the cell
Metaphase II (see picture in notes)
- spindle fibers align chromosomes at the cell of the equator - each chromosome still has 2 sister chromatids
What is crossing over?
- when homologous pairs line up opposite of each other at the equator of the cell. Parts of the chromatids can become twisted around each other - this results in a new combination of alleles
MEIOSIS The process by which 1.———- (sex cells) are produced. In males, gametes are called 2.——-, and in females, they are called 3.——. Meiosis occurs in two stages, 4. ———— and 5.—————. Meiosis reduced the number of chromosomes in the gamete to 6.—— the number of chromosomes in the parent's body cells. When 7.——————- (the union of two gametes) occurs, a zygote is formed. Fertilization restores the original number in the resulting zygote.
1. Gametes 2. Sperm 3. Eggs 4. Meiosis I 5. Meiosis II 6. Half 7. Fertilization
Meiosis II Key Take-Aways: Sexual reproduction is the production of 1.———- cells and the fusion of two of those cells to form the diploid cell. Before sexual reproduction can occur, the number of chromosomes in a diploid cell must decrease by 2.——. Meiosis produces cells with half the number of 3.—————- as the original cell
1. Haploid 2. Half 3. Chromosomes
At the end of telophase I, one parent cell has divided into - daughter cells
2
End result:
2 cells that each have a unique combination of 23 duplicated chromosomes coming from both parents
If a bat has 44 chromosomes in its somatic cells, how many chromosomes will be present in its gametes?
22
How many chromosomes do humans have in each of their sex cells?
23
In the nucleus of a human parent sperm cell float — pairs of chromosomes
23
Inside the egg or sperm breaks, open releases its nucleus of — chromosomes
23
If a camel has 70 chromosomes in its body cells, how many chromosomes will be present in its sex cells?
35
End result:
4 haploid cells with a combination of chromosomes from both mother and father
If a dog has 39 chromosomes in its haploid cells, how many chromosomes will it have in its diploid cells?
78
At the end of interphase I, how many total chromosomes as the parent cell nucleus have?
92
VOCAB Chromosomes
A condensed DNA molecule with part (or all) of the genetic material of an organism
Metaphase 1 (see picture in notes)
- homologous chromosomes line up in the middle of the cell - chromosomes (some from father and some from mother) are lined up along the equator
If a monkey has 21 chromosomes in its gametes, how many chromosomes will be present in its somatic cells?
42
How many chromosomes do humans have in each of their body cells?
46
Somatic Cells
AKA: Body Cells Found in body tissues and organs DNA in body cells are NOT passed to offspring Ex: nerve cell
2 types of chromosomes:
Autosomes and sex chromosomes
What is the biological sex of someone with an XX sex chromosome?
Female
XX:
Female
Cells are haploid:
Gametes
Refers to a cell that only has half of the chromosomes that are normally present in the organisms somatic cells
Haploid
A diagram that shows the appearance of chromosome # of an organism
Karyotype
Does mitosis or meiosis occur more frequently in your body?
Mitosis occurs throughout your life meaning it occurs more
Do you think the Y chromosome contains genes that are critical for an organism survival?
No, because females not contain a life chromosome, and they are able to survive
Body Cells (hair & nails):
Somatic Cells:
Another term for body cells
Somatic cells
Form in body cells:
Somatic cells
Formed throughout an organisms life:
Somatic cells
Identical to all of the other cells of similar function:
Somatic cells
Meiosis
Starts with one 2n cell and ends with four n cells Somatic cells —> sex cells (gametes)
Meiosis 1
Prophase 1, Metaphase 1, Anaphase 1, Telophase 1
Crossing over occurs:
Prophase I
Meiosis II
Prophase II, Metaphase II, Anaphase II, Telophase II
Mitosis vs. Meiosis
Purpose: Mit. - to repair damage body cells, growth Mei. - create sed cells that are needed for reproduction
Mitosis vs. Meiosis
Rounds of Cell Division: Mit. - 1 cell division Mei. - 2 cell divisions
Mitosis
Starts with one 2n cell and ends with two 2n cells Somatic cells —> more somatic cells
The cytoplasm is split and forms two cells:
Telophase I
Four (II) individual nuclear membranes begin to form:
Telophase II
Why must meiosis happen twice?
To create a haploid gamete- so that during fertilization (the union of two haploid cells), the full number of chromosomes is restored
What is the purpose of meiosis?
To create haploid gametes that are genetically diverse
A parent sperm or egg cell must divide ——- to produce 4 daughter cells, each having only 1/2 the chromosome number
Twice
The name of the cell creates when a sperm fuses with an egg:
Zygote
2 mechanisms occur during Meiosis 1 which introduce genetic information
Coursing Over and Independent Assortment
Mitosis vs. Meiosis
Creates: Mit. - all the cells in your body ( except sex cells ) Mei - sex cells only ( egg/sperm )
During prophase I, homologous chromosomes are so closely touching that they exchange sections of DNA. This is called ———— ——
Crossing over
What are the two sources of genetic variation that take place during the first meiosis division?
Crossing over and independent assortment
A cell with two (di) of each kind of chromosome:
DIploid
Mitosis vs. Meiosis
Definition: Mit. - process of cell division that forms 2 new cells (daughter cells) each with the same number of chromosomes Mei. - process of cell division which 4 new cells are created - each with half the original number of chromosomes
Refers to a cell that has two sets of chromosomes present
Diploid
Mitosis vs. Meiosis
End Result: Mit. - results in diploid cells (2n) Mei. - results in haploid cells (n)
In meiosis II, the two daughter cells undergo a second complete cell division. The result is —— daughter cells each containing only half of the parent cells original DNA
Four
Interphase
G1: cells grow and perform many of their required cellular functions S: DNA is copied (replicated) G2: makes proteins, grows
Another term for sex cells
Gametes
Egg and Sperm:
Gametes
Sex Cells:
Gametes
gametes vs somatic cells: Another term for sex cells:
Gametes
What is the purpose of meiosis?
Gametes are produced
Mitosis vs. Meiosis
Genetic Diversity?: Mit. - no Mei. - yes
What is the difference between haploid cells and diploid cells?
Haploid cells contain HALF the number of chromosomes as diploid cells
How do homologous chromosomes differ from sister chromatids?
Homo lodges chromosomes, have the same genes, but have different versions of them. Sister chromatids are copies of each other produced by DNA replication.
Each species has a characteristic number of chromosomes per cell
Humans have 23 pairs (46 total)
When does DNA replication occur in the process of meiosis?
Interphase
Is the cell that results from fertilization diploid or haploid?
It is the union of two haploid cells (n + n = 2n)
What is the biological sex of someone with an XY sex chromosome?
Male
XY
Male
Sperm and egg cells are made by a special cell division process called ———-
Meiosis
Separates homologous pairs of chromosomes:
Meiosis I
Separates sister chromatids resulting in half the number of chromosomes per cell:
Meiosis II
Meiosis Review
Meiosis Review
Meiosis end result:
Meiosis produces 4 sex cells that are genetically different from one another and from the original cell
Stage of Meiosis: Sister (II) chromatids line up in the Middle of the cell:
Metaphase II
Through the process of ———-, the egg cell undergoes its first regular cell division
Mitosis
Gametes
AKA: Sex Cells Eggs (female); Sperm (male) DNA in gametes can be passed to offspring
Paired homologous chromosomes separate:
Anaphase I
Sister (II) chromatids are separated (Apart):
Anaphase II
What is the difference between an autosome and a sex chromosome?
Autosomes directly affect only body trades, whereas sex chromosomes directly affect the sexual characteristics of an organism
Organism —> house fly
Chromosome # for Somatic Cells —> 12 Chromosome # for Gametes —> 6
Organism —> pea
Chromosome # for Somatic Cells —> 14 Chromosome # for Gametes —> 7
Organism —> honeybee
Chromosome # for Somatic Cells —> 32 Chromosome # for Gametes —> 16
Organism —> cat
Chromosome # for Somatic Cells —> 38 Chromosome # for Gametes —> 19
Organism —> rat
Chromosome # for Somatic Cells —> 42 Chromosome # for Gametes —> 21
Organism —> humans
Chromosome # for Somatic Cells —> 46 Chromosome # for Gametes - > 23
Organism —> fruit fly
Chromosome # for Somatic Cells —> 8 Chromosomes # for Gametes —> 4
