BIO 189: Chapter 9- Sexual Reproduction and Meiosis

What is asexual and sexual reproduction?

Asexual: Without involvement of another organism (genetically identical)

Sexual: Requires combination of genetic material from both

What is a ploidy?

The number of full sets of chromosomes in a cell or an organism

What are haploids and diploids?

Haploid: one set of chromosomes

Diploid: two sets of chromosomes

Most somatic body cells in sexually reproducing organisms are _____?

Diploid

Gametes and asexually reproducing organisms are ___?

Haploids

What are some pros and cons of asexual reproduction?

Pros: No need to find a mate & can maintain “good” genes

Cons: Reduced genetic variety which could lead to extinction

What are some pros and cons of sexual reproduction?

Pros: Increased genetic diversity and allows for evolution

Cons: Need to find/attract a mate and genomes become diluted

The offspring of sexually reproducing organisms are _______ but not identical to parents or siblings

genetically related

Why is genetic diversity good?

Sexual reproduction increases diversity

High genetic diversity allows organisms to adapt to different circumstances

Adaption increases long term survival chances

What are the differences between mitosis and meiosis?

Mitosis: Somatic cells are created, only used to divide, results in two identical diploid daughter cells, important for growth and development

Meiosis: Germ line cells produce gametes, starts as one diploid cell and ends with four non-identical haploid cells, important for sexual reproduction

Gametes have only _____ ________ instead of 23 pairs of homologous chromosomes

23 chromosomes

Meiosis is ___________ while fertilization is ________

Reduction to haploid and return to diploid

DNA duplicates how many times and before what?

Once and before mitosis and meiosis

Mitosis has ____ cell division and meiosis has ___ cell divisions

One and Two

Interphase in a somatic cell comes before what?

Mitosis

Interphase in a germ-line cell comes before what?

Meiosis

What are the blue chromosomes and what are the red ones?

Red= Maternal

Blue= Paternal

What happens during prophase in both mitosis and meiosis?

Mitosis: Chromosomes condense, centrosomes move to opposite poles, and nuclear envelope disintegrates

Meiosis: Chromosomes condense, homologous chromosomes associate closely, recombination/crossing over occurs

Genes are located at the same part (___) of both homologous chromosomes

locus

What does recombination/crossing over do?

Physically exchanges regions of chromosomes when they associate at this stage

What happens during metaphase in both mitosis and meiosis?

Mitosis: All individual chromosomes align single file along metaphase plate

Meiosis: Homologous chromosome pairs align as pairs along metaphase plate

What happens during anaphase in both mitosis and meiosis?

Mitosis: Sister chromatids are pulled apart becoming daughter chromosomes

Meiosis: Homologous chromosomes are pulled apart

What happens during telophase & cytokinesis in both mitosis and meiosis?

Mitosis: Daughter chromosomes are enclosed in two nuclei and chromosomes decondense

Meiosis: Chromosomes are enclosed in two nuclei and chromosomes decondense (becoming haploids)

What does cross-over/recombination do?

Increases genetic diversity by making unique chromosomes with new combinations of maternal and paternal alleles

During metaphase I homologous pairs are in what?

Random alignment and independent assortment

What is the difference between the formation of monozygotic (identical) and dizygotic (fraternal) twins

Monozygotic: A single zygote produces two embryos

Dizygotic: Two zygotes form two different embryos at the same time

What are most chromosomal disorders caused by?

Errors during Meiosis

What is an error during meiosis (nondisjunction in meiosis I)?

All 4 gametes and 100% of zygotes will have abnormalities

What is an aneuploidy?

An unbalanced chromosome number (extra or fewer)

What is monosomic/monosomy and what is it represented by?

A cell is missing a chromosome (n-1)

What is trisomic/trisomy and what is it represented by?

A cell contains an extra chromosome (n+1)

What is an error during meiosis (nondisjunction in Meiosis II)?

2 gametes and 50% of zygotes will have abnormalities

What does having a trisomy 21 and 18 mean?

Trisomy 21: Down Syndrome

Trisomy 18: Edwards Syndrome

What are the different sex chromosome abnormalities?

XXX- Triplo-X

XXY- Klinefelter or XXY syndrome

XYY- Jacobs or XYY syndrome

XO- Turner Syndrome

What does polyploidy mean?

Entire extra sets of chromosomes (most animals do not survive and more tolerated in plants)

Total nondisjunction, occurs in stressful conditions