BSCI 105 Lecture 16: The Central Dogma of Molecular Biology

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chocolatetrout893

16 Dec 2015

School

University of Maryland

Department

Biological Sciences Program

Course

BSCI 105

Professor

Dr.Keller

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Document Summary

Parents pass on variations in appearance and behavior to their offspring like) Heritability offspring resemble parents (phenotype what you look. Phenotypic variation individuals have differences in traits. Heritable variation differences in traits get passed on to offspring. Gene a unit of heritable material that defines a trait. Alleles different versions of a gene that explain variations in a trait (genotype make up of alleles) Somatic cells different versions of a gene that explain variations in a trait two copies (homologous) of every chromosome (diploid 2n = 46 in humans [n is the number of chromosomes]) Gametes have one copy of every chromosome (haploid n = 23: combine to form an embryo with two copies again (back to diploid) Sexual reproduction produces new combinations of heritable variations in traits. Gametic cells have one set of chromosomes. Demonstrated transformation genetic material transferred between strains. Dna as the molecule mediating transformation (not protein) Rna ribonucleic acid (can also form structural molecules and.

Related Questions

Match the term with its correct definition or explanation.

Chromatin

Homologous Chromosomes

Sister chromatids

Diploid

Interphase

S Phase

Synapsis

Crossing Over

Cell Plate

Cleavage Furrow

A. The exchange of genetic material between homologous chromosomes during meiosis I.

B. The pairing or tight association of homologous chromosomes in meiosis I. Results in the formation of a tetrad.

C. Non-identical copies of the same chromosome. Present in all diploid cells, even before replication. These chromosomes are the same length and contain genes for the same characteristics, but may have different alleles for each gene. D.

The period of the cell cycle that includes G1, S phase, and G2. E. A structure that develops during cytokinesis in plants.

F. Condensed chromosomes.

G. An invagination that develops during cytokinesis in animal cells.

H. When an organism has two copies of every chromosome (2n).

I. Two identical copies of a chromosome. These are only present after DNA replication.

J. The phase of the cell cycle when DNA is replicated.

Ploidy refers to the number of complete sets of chromosomes (genes) present in a cell. The number of chromosomes in a complete set is a fixed characteristic of a species. Humans are diploid with two sets of 23 chromosomes. Fruit flies are diploid with two sets of 4 chromosomes. Sexually reproducing organisms are diploid, each somatic cell of an organism has two complete sets ("di" is a prefix indicating 2.). To complete a life cycle and reproduce new members of a species, mating is required. Mating brings a donation from a male and a donation from a female together. However, if the male and female cells remain diploid, the fertilization will result in a tetraploid zygote. In general, these are not viable. A mechanism is needed to form special haploid cells, gametes. The diploid set is split precisely into two complete haploid sets. That mechanism is meiosis.

The complete set of chromosomes of a species is also the complete set of genes of a species, the genome. (Yes, there is a minor contribution from mitochondria and chloroplasts. Inheritance of this information is "cytoplasmic".)

Please answer the following questions:

1. How many chromosomes in a brain cell of a fruit fly? How many chromosomes are in a liver cell of a human? Explain both answers.

2. How many chromosomes are in a fruit fly unfertilized egg? How many chromosomes are in a human egg? Explain both answers.

3. Why is meiosis necessary for sexually reproducing organisms? How many chromosomes are in a human zygote? Relate the two answers.

4. What is a gene allele? Suppose there is a gene called "bingo" and it is present once in a complete haploid set. How many alleles of "bingo" does a diploid individual have? How many copies or versions of the gene "bingo" are present in a diploid individual?

5. Modern DNA sequencing clearly identifies alleles by showing the different DNA sequence of each allele. These alleles may be termed structural alleles (I coined the term for this problem.). Classical genetics only dealt with phenotypes or visible traits. As a result, alleles of genes were identified by functionality, usually normal or non-functional. Using your knowledge of gene structure and gene expression, postulate a relationship between structural alleles and functional alleles. (include relative amounts; more, less, or equal).

1). Explain the significance of the fact that gametes contain half of the chromosome complement of somatic cells. Tell me something about variation, if you have a sibling (if you don't imagine you do) - how is your sibling's genetic make-up similar and/or different from yours? What about your mom and dad?

2). Explain the terms reductional division and equational division. What is reduced or kept equal? To which nuclear divisions do these terms refer?

3). What is the diploid number (2n = ?) of an organism if it has
a) 12 chromosomes at Anaphase of Mitosis?
b) 12 chromosomes at Anaphase I of Meiosis?
c) 12 chromosomes at Anaphase II of Meiosis?

4). Compare/contrast Metaphase I of Meiosis with Metaphase of Mitosis.

5). What are the two mechanisms of variation in Meiosis, and during which stage(s) does each occur?

6). Draw a diagram of a bivalent and label the following parts: centromere, sister chromatids, non-sister chromatids, homologous chromosomes, chiasma.

7). A diploid cell has 1 pair of acrocentric chromosomes (Chromosome 1) and 1 pair of submetacentric chromosomes (Chromosome 2).
Â· Gene X is on Chromosome 1. Gene Y is on the short arm of Chromosome 2 and Gene Z is on the long arm of Chromosome 2.
Â· The maternal chromosomes have the X, y, z alleles, whereas the paternal chromosomes have the x, Y, Z alleles.
Draw these chromosomes, labeling ALL alleles, as they might appear in Metaphase I of Meiosis.

BSCI 105 Lecture 16: The Central Dogma of Molecular Biology

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