Learn and test your biological vocabulary using these 10.1 Meiosis flashcards
Summary list for 10.1 Meiosis
Crossing over
- DNA replication makes a second chromatid in each chromosome in interphase before meiosis.
- Crossing over exchanges pieces of DNA between non-sister homologous chromatids and forms new combinations of alleles on the chromosomes formed in meiosis.
- Chiasmata are the crossing over points.
Chromosomes movements
- Details of chromosome movements in meiosis.
- Homologous chromosomes separate in meiosis I.
- Sister chromatids separate in meiosis II.
- Random orientation of homologous chromosomes in meiosis I leads to independent assortment of alleles.
Student skills and applications
- Drawing diagrams to show chiasmata formed by crossing over.
- show sister chromatids still closely aligned, except at the point where crossing over occurred and a chiasma was formed.
Mindmaps
This diagram summaries the main sections of topic 10.1.
Test if you can draw something like these concept maps from memory.
Exam style question about meiosis
Explaining the movement of chromosomes is an important skill from this topic.
Answer the question below, on a piece of paper, then check your answer against the model answer below.
Describe crossing over and the formation of a chiasma. Credit will be given to labelled diagrams. [4]
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Click the + icon to see a model answer.
Extra exam question on variation due to meiosis. Click to open.
Genetic variation caused by meiosis is an important aspect of this topic.
Answer the question below, on a piece of paper, then check your answer against the model answer below.
Question: Outline the ways in which genetic variation is achieved in gamete production by meiosis. (5 marks).
Outline – important points with an explanation. .
Multiple choice questions
This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding.
START QUIZ!
In which stage of meiosis does crossing over occur and between which structures?
Crossing over (chiasma) occurs in prophase 1 between non-sister chromatids.
Chromatid is the term for the two strands of DNA produced by DNA replication which are joined at the centromere of a chromosome.
The random orientation of homologous chromosomes in meiosis results in which feature of meiosis?
Independent assortment is caused by the random alignment of homologous chromosome pairs during metaphase I, so C is correct.
Crossing over further mixes the alleles of linked genes.
3. In which division of meiosis do;
A) homologous chromosomes separate, and
B) sister chromatids separate?
In metaphase I the homologous chromosomes are in pairs (tetrads) on the equator of the spindle.
In anaphase I the individual chromosomes separate and move to opposite poles of the cell
In metaphase II the double stranded chromosomes line up on the equator of the spindle
In anaphase II the centromeres of each chromosome split and the individual chromatids become separate single stranded chromosomes.
How do the chromosomes become double stranded before the start of meiosis?
DNA replication makes a second strand of DNA forming a second chromatid in each chromosome in interphase before meiosis.
What is the affect of crossing over on the alleles found in chromosomes?
Crossing over causes some alleles to be exchanged from one chromatid to another.
The new chromosomes are different from the original chromosomes.
This increases diversity in offspring.
Which of the following lists the chromosome movements of meiosis in the correct sequence?
Details of chromosome movements in meiosis. ie: Homologous chromosomes line up in pairs, crossing over takes place, homologous chromosomes separate, cell divides, double stranded chromosomes split cells divide again.
Which of these statements describes a difference between meiosis I and meiosis II?
Meiosis II separates sister chromatids
The drawing below shows an image of homologous chromosomes during meiosis and two diagrams drawn by biologists to show chiasmata formed by crossing over.
Which of the diagrams A or B shows the most convincing interpretation and why?
In diagrams of crossing over sister chromatids will be closely aligned, except at the point where crossing over occurs and a chiasma is formed.
In A the chromatids are close together except where one of the sister chromatids from each chromosome crosses over.
Drag and drop activities
Test your ability to construct biological explanations using the drag and drop questions below.
Independent assortment during meiosis creates genetic variation.
Drag an drop the correct word or phrase into the gap to outline how independent assortment occurs.
Prophase 1 equator second centromere randomly Prophase II sister centre separated gamete homologous
In of meiosis, chromosomes pair and become attached by their . The pairs of homologous chromosomes then associate into a bivalent of chromosomes.
In Metaphase 1 of meiosis, the bivalents line up on the spindle at the . Each tertrad orientates and independently of any other set of bivalents.
In Anaphase 1, the bivalents are , any pair can be drawn to either pole independently. The pairs of chromatids later separate during the division of meiosis giving different combinations of chromatids in the .
Homologous chromosomes have identical alleles, inherited from on of the parents. Sister chromosomes have identical genes but may have different alleles and are inherited from the other parent.
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