16 Questions
What happens to the number of cells and chromosomes in the first division of meiosis?
The number of cells doubles and the chromosome number halves
What is the purpose of meiosis?
To produce cells that are genetically unique and contain only half as much DNA
What is a karyotype?
A set of chromosomes arranged by size
What is non-disjunction?
The failure of chromosomes to separate
What is trisomy?
The presence of three homologous chromosomes
What is the notation for Down Syndrome?
47, XX/XY, +21
What is a characteristic of Turner Syndrome?
A particularly short, wide neck
What is a symptom of Down Syndrome?
A single line across the palm (palmar crease)
What is the proportion of adenine (A), thymine (T), guanine (G), and cytosine (C) in DNA?
1(A):1(T), 1(G):1(C)
What is the shape of DNA?
A corkscrew or helix
What is the number of chromosomes in a haploid cell?
23 chromosomes
What determines the sex of an offspring?
The type of sperm cell that reaches the egg
What is the purpose of mitosis?
To produce two daughter cells
What is the process of cell division that reduces the number of chromosomes in gametes?
Meiosis
What are the non-sex related chromosomes?
Autosomes
What is the physical process of cell division that divides the cytoplasm of a parental cell into two daughter cells?
Cytokinesis
Study Notes
DNA Structure
- A nucleotide is the repeating unit of DNA, composed of deoxyribose sugars, a phosphate group, and one of four nitrogenous bases.
- Complementary base pairing occurs between adenine (A) and thymine (T), and between guanine (G) and cytosine (C).
- DNA is made up of a pentose sugar, a phosphate group, and one of four nitrogenous bases, with A, T, G, and C in equal proportions (1:1:1:1).
- DNA has a helical or corkscrew shape.
Chromosomes
- Haploid cells have one set of chromosomes (n = 23) containing 23 chromosomes.
- Diploid cells have two sets of chromosomes (2n = 46) containing 46 chromosomes, with each parent contributing a chromosome to each pair.
- Autosomes are non-sex related chromosomes, with 23 pairs, and 22 pairs are autosomes.
- Sex chromosomes are a set of X and Y chromosomes, determining the sex of an individual, with XX producing a girl and XY producing a boy.
Homologous Chromosomes
- A pair of chromosomes containing the male and female chromosomes with alleles carrying the same gene type, found in the same loci.
- Chromosomes are inherited maternally and paternally.
Cell Division
- Mitosis is a type of cell division occurring in asexual reproduction, resulting in two genetically identical daughter cells from a single parent cell.
- Meiosis is a type of cell division in sexually reproducing organisms, reducing the number of chromosomes in gametes (sperm and egg cells).
- Meiosis consists of two divisions, with the first division resulting in cell doubling but chromosome halving, and the second division similar to mitosis.
Karyotypes
- A karyotype is an individual's complete set of chromosomes, sorted and arranged according to size.
Abnormal Meiosis
- Non-disjunction occurs when chromosomes fail to separate, resulting in daughter cells with abnormal chromosome numbers (22 or 24).
- Trisomy is an abnormality where three homologous chromosomes replace a homologous pair.
- Monosomy is an abnormality where a single chromosome replaces a homologous pair.
Chromosomal Diseases
- Downs Syndrome: 47, XX/XY, +21
- Turner Syndrome: 45, XO
- Klinefelter Syndrome: 47, XXY
- Supermale Syndrome: 47, XYY
- Patau Syndrome: 47, XY, +13
- Edward Syndrome: 47, XX, +18
- Symptoms of chromosomal diseases include:
- Down Syndrome: flattened face, almond-shaped eyes, short neck, small ears, and small hands and feet.
- Turner Syndrome: short, wide neck, broad chest, widely spaced nipples, arms that turn out slightly at the elbows, and low hairline.
Test your knowledge of DNA structure, nucleotides, and complementary base pairing in molecular biology. Understand the composition of DNA and how it's formed.
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