Meiosis Flashcards
How does genetic variation in gametes arise?
It arises from the independent assortment of chromosomes, crossing over, and random fertilization.
How does meiosis affect the number of chromosomes from parent to daughter cells?
Meiosis reduces the number of chromosome sets from diploid to haploid.
What is the role of gametes in plants and animals that reproduce sexually?
Reproductive cells called gametes are the vehicles that transmit genes from one generation to the next.
How do fertilization and meiosis cause unique offspring?
During fertilization, male and female gametes unite, passing genes from both parents to their offspring. Because genes are inherited from two parents, the offspring has a unique combination. This uniqueness is in large part due to meiosis followed by fertilization.
Are gametes diploid or haploid?
Haploid.
What is a karyotype?
A display of the chromosome pairs of a cell, arranged by size and shape.
Describe the characteristics of the human karyotype.
There are 46 chromosomes: 2 chromosomes of each of 23 types. The homologous chromosomes have the same length, centromere position, and gene arrangement.
What are autosomes?
The autosomes are the non-sex chromosomes (1-22).
What are homologous chromosomes?
A couple of homologous chromosomes are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization. They have the same length, centromere position, and gene location (though the genes are not identical).
How do somatic cells reproduce?
In humans, somatic cells (2n) divide by mitosis and contain 23 pairs of chromosomes (46 in total)–a maternal set and a paternal set–and are diploid (2n).
How do germ cells reproduce?
In humans, germ cells (2n) divide by meiosis and result in gametes that contain a single set of chromosomes: gametes are haploid (n).
How does a zygote divide?
Through mitosis.
What are sister chromatids?
A sister chromatid refers to the identical copies formed by the DNA replication of a chromosome, with both copies joined together by a common centromere. In other words, a sister chromatid may also be said to be ‘one-half’ of the duplicated chromosome.
What is the difference between sister chromatids and non-sister chromatids?
Sister chromatids are the duplicated chromosome themselves, and they contain the exact same alleles. Non-sister chromatids are the chromatids of the homologous chromosome, and they may contain different alleles.
What happens in interphase?
In interphase (S phase), chromosomes duplicate, yielding sister chromatids.
What happens in prophase I?
The centrosomes move, the spindle forms, duplicated chromosomes pair, and crossing over happens.
What happens in metaphase I?
Pairs of homologous chromosomes attach to the metaphase plate. Independent assortment happens here.
What happens in anaphase I?
Homologous chromosomes separate and move toward opposite poles–the sister chromatids remain paired.
What happens in telophase I and cytokinesis?
The cytoplasm divides, and the cleavage furrow forms–each chromosome consists of two sister chromatids.
What is the overall goal of meiosis I?
To separate homologous chromosomes.
What is crossing over?
Crossing over is a mechanism by which you can add additional genetic variation because the chromosome from mom and the chromosome from dad are swapping information.
What is independent assortment?
Independent assortment is the process where the chromosomes move randomly to separate poles during meiosis. A gamete will end up with 23 chromosomes after meiosis, but independent assortment means that each gamete will have 1 of many different combinations of chromosomes.
In which phase of meiosis does the cell go from diploid to haploid?
Teleophase I/cytokinesis.
Which processes in meiosis introduce genetic variation?
Crossing over and independent assortment.
