3.2 Chromosomes

list mechanisms by which a species chromosome number can change

-chromosome splitting will increase the number of chromosomes -chromosome fusing will decrease the number of chromosomes

Distinguish between a Karyogram and a karyotype

A Karyogram is a graphical/photograph representation of the karyotype. A Karyotype is the characteristics of the chromosomes of an individual (number, type, shape)

Describe the structure and function of plasmid DNA

A plasmid is an extra piece of DNA that is circular and naked, smaller than the main nucleoid DNA, replicates independently of the nucleoid DNA, not found in all prokaryotic cells, can be shared between Bacteria, and often contains genes for antibiotic resistance

Outline the advancement in knowledge gained from the development of autoradiography techniques

Autoradiography is used to make an image of a radioactive substance. The technique is used in cellular and molecular biology to visualize structures. For example, autoradiography can be used to visualize chromosomes, bands of DNA in electrophoresis gels, tissue samples, and single cells.

State an advantage of being diploid

Being diploid means you have two copies of each chromosome, and thus have 2 copies of each gene that the chromosome contains. So, if one of the chromosomes carries a detrimental allele of a gene, there's a second copy of the gene whose allele may be able to counter the affects of the negative version.

Outline sex determination by sex chromosomes

Biological sex is determined by which sex chromosomes are present either XX= female or XY=male. The male parent determines the sex of the offspring by either passing a Y (male) or another X (female) chromosome onto their child

Outline conclusions drawn from the images produced by Cairn's autoradiography technique

Cairns was able to see that Prokaryotic chromosomes are circular. He also observed DNA replication occurring at the replication fork.

List the characteristics by which chromosomes are arranged in the Karyogram

Chromosomes are photographed and arranged by size (largest to smallest), banding pattern and centromere position.

List 3 ways in which the types of chromosomes within a single cell are different

Chromosomes within a cell are different in size (number of base pairs), which genes they carry, sequence of nitrogenous bases, location of the centromere, and the banding pattern when stained.

Describe the use of a karyogram to diagnose Down Syndrome

Down Syndrome is caused by a nondisjunction of chromosome #21 (trisomy 21) resulting in three chromosome #21, which can be seen in a Karyogram.

List example haploid cells

Eggs and sperm are haploid cells

Describe the structure of eukaryotic DNA and associated histone proteins during Interphase (chromatin)

Eukaryotic DNA is linear and associated with histone proteins in a structure called the nucleosome. During Interphase, the DNA is not supercoiled into chromosomes, it is in a loose form called chromatin.

Outline the formation of a diploid cell from two haploid gametes

Gametes are haploid, which means they have ONE complete set of chromosomes. When the gametes fuse during fertilization, the 2 sets of chromosomes combine to make a diploid zygote

Define haploid

Haploid means that the cell or organism contains only 1 set of chromosomes, thus there are no chromosome pairs

Compare the genetic material of prokaryotes and eukaryotes

In prokaryotes, there are no intron sequences, the DNA is one chromosome, and there is one DNA replication start point. (also naked, circular, plasmids may be present, and found in the nucleoid region). In eukaryotes the DNA is linear inside a membrane bound nucleus, has many origins of replication, and has intron sequences.

Define "naked" in relation to prokaryotic DNA

Naked means the DNA is not associated with proteins. In Eukaryotes, the DNA coils around proteins called histones to form structures called Nucleosomes which doesn't happen in Prokaryotes.

Describe the structure and function of nucleoid DNA

Prokaryotic cell DNA can be found in two locations: 1. The nucleoid which has the main DNA of the cell inside (DNA isn't enclosed in a membrane, it is found freely in the cytoplasm, DNA is one loop and is not wrapped around proteins which explains why its naked)

Explain why the chromosome number of a species doesn't indicate the number of genes in a species

The # of chromosomes doesn't indicate the # of genes. It's possible to have one large chromosome with many genes or many smaller chromosomes with fewer genes. Likewise, its possible to have large chromosomes with relatively few genes or smaller chromosomes packed full of genes.

Explain why the typical number of chromosomes in a eukaryotic species an even number

The reason why most eukaryotic organisms have an even number of chromosomes is sexual reproduction in which each parent gives one set of chromosomes, resulting in an even number in the offspring. For example: Parent 1 = n = 13 Parent 2 = n = 13

Outline the structure and function of the 2 human sex chromosomes

The x-chromosome is the larger of the two sex chromosomes; a length of 156 base pairs containing 1,805 genes. While the y chromosome is much smaller and the length is only 57 million base pairs and 460 genes.

Describe the relationship between the genome size of a species and the species' complexity in structure, physiology, and behavior.

There is a lot of variety of genome size. Usually Eukaryotes have larger genomes than prokaryotes. But, the genome size doesn't appear to correlate to a species "complexity" - Homo sapiens have around 21k genes - E coli bacteria have around 4.2k genes - Rice plants (Oryza Sativa) has around 38k genes

Describe Cairn's technique for producing images of DNA molecules from E. coli

Cairn's radioactivity labeled DNA to produce images of the molecule, allowing humans to visualize and measure the length of DNA. 1. DNA was replicated many times in the presense of radioactive thymine. As a result, the DNA noe contained radio active thymine nucleotides. 2. The radioactive DNA was left for some time, covered with a photogenic film. The radioactive thymine exposed the film. 3. This radioactivity made a image of DNA, specifically the circular DNA in a bacterial cell

Define diploid

Diploid means the cell or organism contains two sets of chromosomes, one from each parent

Define homologous chromosomes

Homologous chromosomes are two chromosomes, one of paternal origin and one of maternal origin.

Explain the relationship between the number of human and chimpanzee chromosomes

Humans have 46 chromosomes and chimpanzees have 48 chromosomes. There's evidence that the 2 chimp chromosomes fused together to make one human chromosome (chromosome #2 in humans)

State the number of nuclear chromosome types in a human cell

In the nucleus of a human cell there are 23 types of chromosomes. Males would have an additional type, the y chromosome. There are 22 autosomes and 2 types of sex chromosomes.

State the chromosome number and type is a distinguishing characteristic of a species

Organisms with differing numbers of chromosomes are not likely to interbreed, thus all the members of a species will have the same number of chromosomes.

State a similarity and difference found between pairs of homologous chromosomes

Similarities include the genes at the same loci, mostly a similar DNA base sequence, length (in base pairs), centromere location, and staining pattern. Differences include: a different origin (one from mom vs. dad), different alleles (due to slight changes in base sequences of a gene).

State the human cell diploid number

Somatic human cells have a diploid number of 2n = 46 chromosomes

Explain why chromatin DNA in interphase is said to look like "beads on a string"

The basic unit of chromatin is the nucleosome connected by sections of linker DNA. The structure gives the appearance of "beads on a string." Each nucleosome is made of 8 histone proteins that wrap two turns of DNA.

State the human cell haploid number

The eggs and sperm of humans are haploid thus n=23 chromosomes

State the minimum chromosome number in eukaryotes

The minimum chromosome number in eukaryotes is 2n = 2. The "jack jumper ant" Australian daisy both only have two chromosomes per cell.

Deduce the sex of an individual given a Karyogram

XX= Female and XY= male that is the last chromosome pair

Describe the process of creating a karyogram

a cell is "frozen" in metaphase of mitosis by the application of chemicals that disrupt the mitotic spindle. A hypotonic solution is added, water enters the cell causing it to swell and burst, separating the chromosomes from each other. The chromosomes are stained and viewed with a microscope. A photograph of the chromosomes is taken for organization.