Unit 8 Lesson 2: Genetic Variation from Meiosis Flashcards
The passing of genetic information from one generation to the next is called
heredity.
heredity
the passing of genetic material found in chromosomes from parents to offspring
This genetic material is passed to offspring from each parent in the form of
alleles, which are alternative forms of a gene.
. However, the genes may not be an exact mix of the parents’ alleles because of
variations
inheritable genetic variations
changes in genetic material that can be passed to offspring
importance of inheritable genetic variations
These inheritable genetic variations create differences between organisms in a species and contribute to diversity.
How does inheritable genetic variations happen
There are many causes of genetic variation, but one of them happens during meiosis.
What is DNA
DNA (deoxyribonucleic acid) is a molecule that contains the instructions that make each organism unique.
When is DNA passed down and does every living cell contain DNA
Every living cell contains DNA, and the DNA is passed along from adults to offspring during the process of reproduction.
Some organisms replicate asexually. How do organisms like bacteria repliacate
These organisms include bacteria that can produce offspring through cell division.
. Asexual reproduction can also include a process called budding, whats thay
Asexual reproduction can also include a process called budding, where a new organism starts growing out of the body of the parent organism.
What is the realstionship between the DNA of the parents and offspring of asexual reproduction
As a result, in both forms of asexual reproduction, offspring have the same DNA as the parent.
What is the realstionship between the DNA of the parents and offspring of sexual reproduction
Other organisms replicate sexually. These offspring inherit DNA from both parents, resulting in new, unique combinations of traits.
Genetic variation can be a result of meiosis. What is Meiosis
Meiosis is a type of cell division that in two phases will result in four daughter cells, each with half the number of chromosomes of the parent cell.
Why is Meiosis is important for sexual reproduction
Meiosis is important for sexual reproduction because it produces gametes
gametes
sex cells, which are egg and sperm cells
How much chromosomes do Gametes have
. Gametes have half the number of chromosomes that body cells contain. They are haploid
haploid
the state of having half the number of chromosomes as compared to body cells. “half the chromosomes.”
How does a gamete create pairs o chromoomes
A gamete unites with another of the opposite sex to create pairs of chromosomes.
Why is it important to have sex cells that only have half the number of chromosomes? Most human cells contain 46 chromosomes found in pairs. What would happen If two body cells, each containing the full number of chromosomes, are joined together?
If two body cells, each containing the full number of chromosomes, are joined together, the resulting cell would have 92 chromosomes instead of the usual 46. This would result in an entirely different organism!
Why is it important to have sex cells that only have half the number of chromosomes? Most human cells contain 46 chromosomes found in pairs.
However, if a sperm cell only has 23 chromosomes (haploid) and the egg cell also has 23 , when they join, the offspring’s cells will have: 23+23=46 chromosomes.
Meiosis is a two-phase process:
Phase I and Phase II.
What occurs during Phase I of Meiosis
Genetic variation occurs in Phase I.
What happens during Phase II of meiosis
Phase II is an equal division of the chromosomes because the set of chromosomes in each daughter cell are just divided into two identical cells.
What does the cell do to prepare for meiosis
In preparation for meiosis, the cell begins to grow and replicate its DNA during interphase.
After interphase, meiosis I completes four phases:
prophase I, metaphase I, anaphase I, and telophase I.
What does Meiosis I begin with and what does it end with
Meiosis I begins with diploid cells and ends with haploid cells.
(Prophase I) What happens during prophase I
During prophase I, the copied chromosomes begin to condense and align with their homologous partners.
(Prophase I) homologous chromosomes
a set of nonidentical chromosome pairs that are received from the sperm and the egg
(Prophase I) Are homologous chromosomes the same as sister chromatids
These are not the same as sister chromatids, which form while DNA is being replicated in the cell. One chromosome comes from the egg and one from the sperm.
(Prophase I) Because the homologous partner is similar in size and has similar genes, the pair of chromosomes may exchange segments in a process known as
crossing over.
crossing over.
the process that occurs when genetic information is swapped between homologous chromosomes
(Prophase I) What happens towards the end of prophase I
Toward the end of prophase I, the nuclear membrane starts to break down and spindles that will aid in arranging the chromosomes and then dividing them grow from each side of the cell.
What do Homologous chromosomes start to do during metaphase I
Homologous chromosomes start to align in the center of the cell during metaphase I.
(metaphase I) What will determine which set of genes will end up in spefic gametes
The lining up of the chromosome pairs will determine which of the set of genes will end up in specific gametes.
What will reuslt in different gametes haveing different sets of homologues
This (the lining up) will result in different gametes having different sets of homologues.
What happens during anaphase I
In anaphase I, the homologues are pulled apart and moved to opposite sides of the cell.
What are the sister chromatids like during the first phase of meiosis. And what does the sister chromatids being intact mean
Remember during the first phase of meiosis, the sister chromatids are still intact making each daughter cell have the same amount of genetic material as the parent cell.
When will the sister chromatids be pulled aprt into daughter cells
It is not until phase II that the sister chromatids are pulled apart into daughter cells that have half of the genetic material.
What happens during the telophase I
During telophase I, the nuclear membrane reforms and preparations begin for phase II of meiosis.
What is Cytokinesis
Cytokinesis, or the physical division into two haploid daughter cells
When does Cytokinesis happen
Cytokinesis, or the physical division into two haploid daughter cells, usually happens at the same time as telophase I.
Then without the process of copying DNA, the cells go into a
shorter phase II.
What occurs during phase II
The same phases (prophase, metaphase, anaphase, and telophase) occur during phase II of meiosis
What different about phase II
during this phase, the sister chromatids are now split into separate chromatids.
What are the cells like during Phase II
During phase II, the cells are haploid but with two copies of each chromosome
What happens after phase II
After phase II, each daughter cell is haploid with one copy of each chromosome, meaning that it has half the genetic material as the parent cell.
What happens in interphase 1
In interphase 1, chromosomes replicate forming sister chromatids.
What happens during prophase I
During prophase I, homologous chromosomes align and may exchange non-sister chromosome segments in a process known as crossing-over.
During prophase I, homologous chromosomes align and may exchange non-sister chromosome segments in a process known as
crossing-over.
During prophase I, homologous chromosomes align and may exchange non-sister chromosome segments in a process known as crossing-over. What patter does this echange happen
This exchange occurs in a crisscross pattern and typically between different alleles, or versions, coding for the same gene.
What does it mean when the sister chromatids move into the gamete cell
When the sister chromatids move into the gamete cells, they will now have DNA combinations that did not exist before.
Waht does crossing over do
Crossing-over creates new genetic variations that can be passed to offspring.
What happens during metaphase I - anaphase I
During metaphase I, homologous chromosomes line up randomly and are separated independently of each other in anaphase I.
What effect does the sorting of one pair of homologous chromosomes have on the sorting of another
The sorting of one pair of homologous chromosomes does not affect the sorting of another.
The sorting of one pair of homologous chromosomes does not affect the sorting of another. This distribution, known as the
independent assortment of genes,
independent assortment
the sorting of one pair of homologous chromosomes does not affect the sorting of another
What does indepednet assortment result in
This distribution, known as the independent assortment of genes, results in gametes that have differing combinations of chromosomes from the parents, which also contributes to genetic variation.
Meiosis plays an important role in
genetic variation of species.
Genetic variation is beneficial because it can increase the
survival rate of the population.
In meiosis, the parent cell has 46 chromosomes and the four daughter cells each have 23 chromosomes. Why are only half of the chromosomes from the parent cell passed onto the daughter cells in meiosis?
The reason is to increase genetic diversity in gametes.
What does the inheritance of only half of the chromosomes to the daughter cells lead to
The inheritance of only half of the chromosomes to the daughter cells leads the daughter cells to have a greater genetic diversity within each other.
The inheritance of only half of the chromosomes to the daughter cells leads the daughter cells to have a greater genetic diversity within each other. Why is that
This is because, after crossing over and independent assortment, the more you separate the chromosomes, the more genetic diversity there will be.
If the full chromosome was passed onto the daughter cells after meiosis II, what would ahppen
hen each daughter cell would still have all of the genes of the parent cell, leading to two pairs of genetically identical daughter cells rather than genetically diverse daughter cells.
Why is the process of meiosis important for sexual reproduction?
Meiosis ensures that sex cells contain only half the chromosomes of the organisms. When the sex cells are joined, there will not be more chromosomes than normal for the organism.
Describe why the process of crossing-over is important.
Crossing-over results in new combinations of DNA that did not exist before. The process ensures increased genetic variations in species and a greater chance of survival.
In which phase does crossing-over occur?
prophase I
What occurs during metaphase I that contributes to genetic variation? Explain how this leads to genetic variation in offspring.
Independent assortment of genes is when the sorting of one pair of homologous chromosomes does not affect the sorting of another. It results in gametes that have differing combinations of chromosomes from the parents.
Meiosis results in four genetically diverse daughter cells. What would happen if chromosome reduction did not take place in meiosis II? What impact would this have on the genetic diversity of the population?
The result would be two pairs of genetically identical daughter cells. This would reduce genetic diversity in the population.
How do inheritable genetic variations occur during meiosis?
Meiosis creates inheritable genetic variations in two ways. One, when crossing-over occurs, it creates new combinations of genetic material that did not exist before. Two, the independent assortment of chromosomes occurs where the sorting of one chromosome is unrelated to the sorting of another.
Crossing-over and independent assortment during both phases of meiosis results in which of the following?
identical chromosomes in two daughter cells
identical chromosomes in four daughter cells
genetic variation in two daughter cells
genetic variation in four daughter cells
genetic variation in four daughter cells
Heredity
Heredity is the passing of genetic material, found in chromosomes, from parents to offspring.
How are gametes for each parent produced?
Through the cellular process of meiosis, gametes are produced for each parent.
Wha todes it mean When the gamete of one parent combines with the gamete of the other parent,
When the gamete of one parent combines with the gamete of the other parent, each parent essentially gives half its chromosomes to the offspring, resulting in genetic variations inherited by the offspring.
inheritable genetic variations
changes in genetic material that can be passed to offspring
What effects do events such as crossing-over and independent assortment have
Events such as crossing-over and independent assortment usually create positive or neutral genetic variations in gametes, leading to variety in offspring.
karyotype
a visual representation of the chromosomes within a cell
What are Autosomal traits
Autosomal traits are those that are found on chromosomes 1 to 22, which are the non-sex chromosomes, or autosomes.
How are male and females affeced by autosomal traits
Males and females are equally affected by any autosomal trait, such as freckles.
What the 23rd chromsome
The 23rd chromosome is known as the sex chromosome and is made up of either two X chromosomes for a female or an X chromosome and a Y chromosome for a male
One common meiosis error is known as
nondisjunction
When does nondisjunction occur
This occurs when one or more pairs of homologous chromosomes or sister chromatids do not separate normally during anaphase I or II.
Nondisjunction during meiosis results in gametes having
too few or too many chromosomes.
Wahts the Turner’s Syndrome
For example, Turner’s Syndrome is a rare disorder caused by nondisjunction of the X sex chromosomes. In this case, the resulting female offspring has only one X chromosome or part of the second X chromosome is missing.
Whats it like for a women with Tuner Syndorme
Women with Turner Syndrome can be shorter than average height, have heart or developmental defects, and are infertile.
Other nondisjunction disorders include
Down Syndrome (trisomy, or an extra copy of a chromosome is present in chromosome, 21), Edwards Syndrome (trisomy 18), and Klinefelter Syndrome (extra X chromosomes in males).
Why are females and males equally affected by autosomal traits?
Autosomes are the chromosomes that are the same in both males and females. Autosomal traits are not related to the sex chromosomes and will normally affect both sexes the same.
What error occurs during meiosis that shows an offspring’s karyotype as having too many or too few chromosomes due to abnormal division during meiosis?
nondisjunction
