Chapter 14 Study Guide Biology

ABO blood group

(Codominance) Determined by a gene with three alleles: I^A, I^B, and i. Ex: if a genotype had both A and B, then the phenotypes for both will be expressed.

Colorblindness

(sex-linked inheritance) -Colorblindness only needs to be present on the X chromosomes for males, but need to be present in BOTH X chromosomes for females.

Rh Blood Group

(simple dominance) -The allele for Rh factor comes in two forms: Rh+ and Rh-. -Rh+ is dominant, so an individual with both alleles (Rh+/Rh-) is said to have Rh positive blood. -Rh negative blood is found in individuals with two recessive alleles (Rh+/Rh-).

MC1R

(simple dominance) A gene known as MC1R helps determine skin and hair color. Melanocortin 1 Receptor -Some of MC1R's recessive alleles produce red hair. An individual with red hair usually has two sets of these recessive alleles, inheriting a copy from each parent. -Dominant alleles for the MC1R gene help produce darker hair colors.

Cat and fur

(x-chromosome inactivation) In cells in some parts of the body, one X chromosome is switched off. In other parts of the body, the other X chromosome is switched off. As a result, the cat's fur has a mixture of orange and black spots. Male cats, which have just one X chromosome, can have spots of only one color. If a cat's fur has three colors—white with orange and black spots, for example—you can almost be certain that the cat is female.

karyotype

A karyotype shows us the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size. -To see human chromosomes clearly, cell biologists photograph cells in mitosis, when the chromosomes are fully condensed and easy to view. -Scientists then cut out the chromosomes from the photographs and arrange them in a picture known as a karyotype.

gel electroporesis

A mixture of DNA fragments is placed at one end of a porous gel. When an electric voltage is applied to the gel, DNA molecules—which are negatively charged—move toward the positive end of the gel. The smaller the DNA fragment, the faster and farther it moves. The result is a pattern of bands based on fragment size. Specific stains that bind to DNA make these bands visible.

1000 genomes project

A project which studied the genomes of 1000 people from geographically different areas in order to produce a detailed catalogue of human variation.

Reading DNA

After the DNA fragments have been separated, researchers can read, or sequence, it. Single-stranded DNA is placed in a test tube containing DNA polymerase—the enzyme that copies DNA—along with the four nucleotide bases, A, T, G, and C. The DNA polymerase uses the unknown strand as a template to make one new DNA strand after another. Researchers also add a small number of bases that have a chemical dye attached. Researchers then separate these fragments, often by gel electrophoresis. The order of colored bands on the gel tells the exact sequence of bases in the DNA.

Human DNA and other genetic elements

As much as half of our genome is made up of DNA sequences from viruses and other genetic elements within human chromosomes. More than 40% of our proteins are similar to proteins in organisms such as fruit flies, worms, and yeast.

Bioinformatics

Bioinformatics combines molecular biology with information science. It is critical to studying and understanding the human genome. Bioinformatics also launched a more specialized field of study known as genomics

What techniques are used to study human DNA?

By using tools that cut, separate, and then replicate DNA base by base, scientists can now read the base sequences in DNA from any cell. In the 1970s, scientists found they could use natural enzymes in DNA analysis. Scientists can now read the base sequences in DNA by using these enzymes to cut, separate, and replicate DNA base by base.

codominant inheritance

Certain alleles are all expressed in the Phenotype, versus having one being compeletly dominant over the other.

Heterozygote Advantage (Sickle cell disease and Malariar).

Certain mutated alleles gives an advantage when fighting environmental factors -People with a sickle cell allele tend to have a much greater resistance against malaria, which is why certain alleles have not died out yet.

How do small changes in DNA molecules affect human traits?

Changes in a gene's DNA sequence can change proteins by altering their amino acid sequences, which may directly affect one's phenotype. There is a direct connection between molecule and trait, and between genotype and phenotype. In other words, there is a molecular basis for genetic disorders. Changes in a gene's DNA sequence can change proteins by altering their amino acid sequences, which may directly affect one's phenotype.

DNA databases

Copies of the human genome DNA sequence, and those of other organisms, are now freely available on the Internet. Researchers and students can browse through databases of human DNA and study its sequence. More data is added to these databases every day.

Huntington's disease

Huntington's disease is caused by a dominant allele for a protein found in brain cells. The allele for this disease contains a long string of bases in which the codon CAG—coding for the amino acid glutamine—repeats over and over again, more than 40 times.

trisomy

If two copies of an autosomal chromosome fail to separate during meiosis, an individual may be born with three copies of that chromosome. This condition is known as a trisomy, meaning "three bodies."

DNA similarity

If you were to compare the genomes of two unrelated individuals, you would find that most—but not all—of their DNA matches base-for-base with each other. On average, one base in 1200 will not match between two individuals. Biologists call these single base differences SNPs, which stands for single nucleotide polymorphisms. Researchers have discovered that certain sets of closely linked SNPs occur together time and time again. These collections of linked SNPs are called haplotypes—short for haploid genotypes.

X-Chromosome Inactivation

In female cells, most of the genes in one of the X chromosomes are randomly switched off, forming a dense region in the nucleus known as a Barr body. -Barr bodies are generally not found in males because their single X chromosome is still active

Simple dominance

Includes dominant or recessive alleles.

Sex-linked inheritance

Inherited from a Sex-linked gene- a gene located on a sex chromosome. Ex: Genes on Y chromosomes only effect males.

restriction enzymes

Many bacteria produce restriction enzymes that cut DNA molecules into precise pieces, called restriction fragments that are several hundred bases in length. Of the hundreds of known restriction enzymes, each cuts DNA at a different sequence of nucleotides. For example, the EcoRI restriction enzyme recognizes the base sequence GAATTC. It cuts each strand between the G and A bases, leaving single-stranded overhangs, called "sticky ends," with the sequence AATT. The sticky ends can bond, or "stick," to a DNA fragment with the complementary base sequence.

Cystic fibrosis (CF

Most cases result from the deletion of just three bases in the gene for a protein called cystic fibrosis transmembrane conductance regulator (CFTR). As a result, the amino acid phenylalanine is missing from the protein. CFTR normally allows chloride ions (Cl−) to pass across cell membranes. The loss of these bases removes a single amino acid—phenylalanine—from CFTR, causing the protein to fold improperly. The misfolded protein is then destroyed.

Identifying and sequencing genes

Much of today's research explores the data from the Human Genome Project to look for genes and the DNA sequences that control them. By locating sequences known to be promoters—binding sites for RNA polymerase—scientists can identify many genes. Shortly after a promoter, there is usually an area called an open reading frame, which is a sequence of DNA bases that will produce an mRNA sequence. Other sites that help to identify genes are the sequences that separate introns from exons, and stop codons located at the ends of open reading frames.

Turner's syndrome

Nondisjunction of the X chromosomes can lead to a disorder known as Turner's syndrome. A female with Turner's syndrome usually inherits only one X chromosome. Women with Turner's syndrome are sterile, which means that they are unable to reproduce. Their sex organs do not develop properly at puberty.

Wet and dry earwax

People of African and European ancestry are more likely to have wet earwax—the dominant form. Those of Asian or Native American ancestry most often have the dry form, which is recessive. A single DNA base change from guanine (G) to adenine (A) in the gene for a membrane-transport protein causes this protein to produce dry earwax instead of wet earwax. This is called an SNP (single nucleotide polymorphism)

"Shotgun" sequencing

Researchers first break up the entire genome into manageable pieces. The base sequences in widely separated regions of a DNA strand are determined. These regions can then be used as markers. Computer programs take the sequencing data, find areas of overlap between fragments, and put the fragments together by linking the overlapping areas. The computers then align these fragments relative to the known markers on each chromosome

Result of Sickle cell Disease

Sickle-shaped cells are more rigid than normal red blood cells, and they tend to get stuck in the capillaries. If the blood stops moving through the capillaries, damage to cells, tissues, and even organs can result.

Human Genome Project

The Human Genome Project was a 13-year, international effort with the main goals of sequencing all 3 billion base pairs of human DNA and identifying all human genes. The Human Genome Project pinpointed genes and associated particular sequences in those genes with numerous diseases and disorders Other important goals included sequencing the genomes of model organisms to interpret human DNA, developing technology to support the research, exploring gene functions, studying human variation, and training future scientists.

GINA (Genetic Information Nondiscrimination Act)

The Human Genome Project worked to identify and address ethical, legal, and social issues surrounding the availability of human genome data and its powerful new technologies.

Chromosomal disorders

The most common error in meiosis occurs when homologous chromosomes fail to separate. This mistake is known as nondisjunction, which means "not coming apart." Nondisjunction may result in gametes with an abnormal number of chromosomes, which can lead to a disorder of chromosome numbers .If nondisjunction occurs during meiosis, gametes with an abnormal number of chromosomes may result, leading to a disorder of chromosome numbers.

automosomes

The remaining 44 human chromosomes , not including the X and Y chromosomes The complete human genome consists of 46 chromosomes, including 44 autosomes and 2 sex chromosomes. -To quickly summarize the total number of chromosomes present in a human cell, biologists write 46,XX for females and 46,XY for males.

Result of Huntington's disease

The symptoms of Huntington's disease, namely mental deterioration and uncontrollable movements, usually do not appear until middle age. The greater the number of codon repeats, the earlier the disease appears, and the more severe are it's symptoms.

Sickle cell disease

This disorder is caused by a defective allele for beta-globin part of hemoglobin, the oxygen-carrying protein in red blood cells. The defective polypeptide makes hemoglobin less soluble, causing hemoglobin molecules to stick together when the blood's oxygen level decreases. The molecules clump into long fibers, forcing cells into a distinctive sickle shape, which gives the disorder its name. (remember- this is caused by a substitution of bases)

Pedigrees

To analyze the pattern of inheritance followed by a particular trait, you can use a chart, called a pedigree, which shows the relationships within a family. -A pedigree shows the presence or absence of a trait according to the relationships between parents, siblings, and offspring. This pedigree show

International HapMap project

To locate and identify as many haplotypes in the human population as possible, the International HapMap Project began in 2002. The aim of the project is to give scientists a rapid way to identify haplotypes associated with various diseases and conditions and to pave the way to more effective life-saving medical care in the future.

Klinefelter's syndrome

Tthe inheritance of an extra X chromosome leads to an interferance with meiosis and usually prevents these individuals from reproducing. *There have been no reported instances of babies being born without an X chromosome, indicating that this chromosome contains genes that are vital for the survival and development of the embryo.

sex chromosomes

Two of the 46 chromosomes in the human genome are known as sex chromosomes because they determine an individual's sex. -Females have two copies of the X chromosome. -Males have one X chromosome and one Y chromosome. All human egg cells carry a single X chromosome (23,X). However, half of all sperm cells carry an X chromosome (23,X) and half carry a Y chromosome (23,Y). *This ensures that just about half the zygotes will be males and half will be females.

Result of Cystic Fibrosis

With cell membranes unable to transport chloride ions, tissues throughout the body malfunction. Children with CF have serious digestive problems and produce thick, heavy mucus that clogs their lungs and breathing passageways. People with one normal copy of the CF allele are unaffected by CF, because they can produce enough CFTR to allow their cells to work properly. Two copies of the defective allele are needed to produce the disorder, which means the CF allele is recessive.

Genes on X and Y chromosomes

X chromosome- has 1200+ genes Y chromosomes- only contains about 140

genomics

the study of whole genomes, including genes and their functions