Chapter 7.2 and Chapter 7.3 Genetics

Why did Gregor Mendel pollinate the plants himself rather than let the plants self-fertilize?

Gregor Mendel Pollinated the plants himself rather than letting them self-fertilize to observe the offspring of when two parent plants with different traits would inherit characteristics. By pollinating the plants himself, Gregor Mendel was able to cross-pollinate instead of self pollinate. In self pollination the offspring will have the same traits as the parents, however through cross pollination there are two parents. By pollinating the plants himself, Mendel was able to learn how inheritance works among plants of various traits, discovering how parents pass down characteristics.

Why did Gregor Mendel pollinate the plants himself rather than let the plants self-fertilize?

Gregor mendel pollinated the plants himself because if they were to self-fertilize, plants would only cross with themselves and each generation would have the same genotype and phenotype. By pollinating the plants himself, he was able to cross plants with different genotypes and phenotypes which cause the phenotypes passed down through each generation to vary. Could study the offspring of two different parents.

Why is a person with Type O blood called a "universal donor"?

Type O-negative blood does not have any antigens. It is called the "universal donor" type because it is compatible with any blood type. Type O individuals have neither A nor B protein on their red cells, and antibodies against type A and type B are present in their plasma. Antigens determine how a blood reciepient reacts to a blood transfusion. If the immune system encounters an antigen not found in the body's cells, the body will fight it off, in type o blood there are no antigens for the body to react to. It is compatible with all blood types because it has no antigens.

X-linked genes/inhertiance:

When a gene is present on an x chromosome but not on the y chromosome it is x-linked. The gene causing the trait or disorder is located on the x chromsome. Inhertiance works differently on males than females. Females need two recessive alleles to have a recessive phenotype, male only need one copy of an x-linked recessive gene for the trait to be expressed. Examples of x-linked inherited conditions: red-green color blindness, hemophilia (disorder where the blood cannot clot properly)

Incomplete dominance:

When two homozygous phenotypes produce a heterozygous phenotype that expresses characteristics between the two homozygous phenotypes. The result is a blended phenotype. For example, crossinnng dominant red flowers with white flowers yields pink flowers.

Fertilization:

fertilization is an organism that has a copy of each gene from each parent, meaning the organism should have two copies of each gene

Monohybrid Cross:

A cross that examines one trait. There are basic types of monohybrid crosses: a homozygous-homozygous cross, a heterozygous-heterozygous cross and a heterozygous-homozygous cross.

Dihybrid cross:

A cross that examines the inheritance of two traits. A heterozygous-heterozygous dihybrid cross results in a phenotypic ratio of 9:3:3:1

homozygous-homozygous

A homozygous-homozygous cross always results in heterozygous offspring because one parent can only donate dominant alleles and the other can only donate recessive alleles. Results in one recessive and one dominant allele whcih is a heterozygous combination. With a dominant allele present in all genotypes, the dominant phenotype will only be expressed.

Pedigree:

A model constructed to study inheritance patterns. A pedigree is a family tree that tracks a trait through multiple generations.

X-inactivation:

A process that prevents double expression of sex-linked traits in females. One x-chromosome in each cell becomes inactive, all descendents of these early cells have the same inactive x. The process does not impact the phenotype of homozygous females since both x chromosomes have the same allele.

Purebred:

A purple flowering pea plant can only reproduce an offspring that has purple flowers as well during self-fertilization. Generation. Synonymous with homozygous, two of he same type, that only have one type of allele. Plants that self-fertilize can only produce the same trait. Hybrid plants mean heterozygous. Monohybrid-one trait, Dihybrid Two Traits.

Punnett Square:

A simple table that predicts all possible offspring genotypes resulting from a specific cross. An easy way to determine the probable outcome of a cross. The model pulls letters that represent a parental genotype apart and places them outside the punnet square showing the segregation of homologous chromosomes and different alleles during meiosis. The assignment of alleles to the empty boxes models fertiliziation. Haploid gametes join to make a diploid zygote. The letter pairs that are joined together represent potential offspring genotypes.

Characteristic:

A special quality or trait that distinguishes an organism from another. These qualities or traits might be common among a specific type of organisms.

Self-fertilization (self-pollination):

A type of fertilization where a parent organism fertilizes itself by using its own sperm or pollen as opposed to that of another organisms.

Gene:

A unit of genetic information that is passed down from a parent organism to its offspring. Genes contain genetic information that instructs cells tto make specific proteins. Traits are not passed down from one generation to the next but the genes are.

How is an allele related to a gene?

Alleles are different forms of a gene. Alleles are sequences of a gene. On a genetic locus, diploid organisms have two alleles one from each parent. The alleles indicate the gene that is expressed.

Carrier:

An individual who is capable of passing down a genetice mutation. May or may not display the symptoms. Carriers are associated with diseases inherited as recessive traits. An individual having one normal allele and one mutated allele does not express the disease.

Why is a person with Type AB blood called a "univeral acceptor"

Both antigens for type A and B blood are present and therefore compatible with the body. Has all antigens that are possible, immune system will respond well to it.

True Breeding:

Crossing an organism with itself over and over again and only producing offspring identical to the parent organization throughout each generation.

Sex- Linked Genes:

Females donate an X-chromsome and males can donate either an X or Y chromosome. Genes located on the sex chromsomes are sex-linked genes. Follow a pattern of inheritance called sex-linked inheritance. They are not always connected to sexual characteristics. Few genes appear on both the x and y chromosomes so males with only one x chromosome express x-linked genes. Female chromosomes go on top of the punnet square and male chromosomes on the left.

Test cross:

Fertilization of genotypes from two different parents. Determining the genotypes when you know the phenotype.

Cross-fertilization (cross-pollination):

Fertilization that occurs between two organisms. The sperm or pollen from one organism fertilizes that of another organism and exchanges of genetic material occur. Multiple organisms and not just one are involved.

Epistasis:

Genes that play a role in being able to alter how another gene expresses itself are epistatic genes. The process by which epistatic genes interfere and change how a gene expresses itself is known as epistasis. For example, in albinism an animal homozygous for albino genes will be white regardless of the phenotypes of other genes.

Genomics:

Genomics is a form of biology that focuses on studying how a particular gene functions. Through genomics, DNA sequences in organisms are analyzed by their functions and structure.

Heterozygous-Heterozygous Cross:

Heterozygous-Heterozygous Cross:Each parent has one dominant allele and one recessive allele. In a heterozygous-heterozygous cross, half the offspring receive a dominant allele adn half receive a recessive allele. This type of cross always results in a 1:2:1 ration. ¼ of offspring will be homozygous dominant, ¼ homozygous recessive, 2/4 hetereozygous genotype. ¾ dominant phenotype and ¼ recessive phenotype.

Heterozygous-Homozygous Cross:

Homozygous pareent donates reecessive alleles to all offspring. The heterozygous parent donates dominant alleles to half the offpsirng and recessive alles to half the offspring. The result are half offspring with heterozygous genotype and half the offspring with homozygous recessive genotype. 1:1 genotypic ratio.

How do the genotypic and phenotypic ratios of the sex-linked traits differ from those of a monohybrid cross?

In sex linked traits, only x-linked genes are expressed. For a male, whatever gene is expressed on the x-chromosome is expressed while on a females, genes are on both chromosomes. Dominant genes are expressed unless there are homozygous recessive. In monohybrid crosses, only the dominant alleles is expressed, a superscript is not expressed and the dominant allele always maskes expression of a recessive allele.

What forms of evidence offer support for Mendel's conclusion that traits are inherited as discrete units from the parental generation?

Mendel's conclusion that traits are inherited as discrete units from the parental generation was proved when he found offsprings of a parental organism that expressed a variety of traits. For example, Mendels crossed two parents with different variations of a traits to observes how traits are inherited. He noticed that the traits of the parental organisms were not blended, altered or diluted in successive generations, and that the offsprings of the plants he observed sometimes had the same genes as the parental organism, but could also sometimes have varying genes. From mendel's experiment, he was able to conclude that traits do not disappear or mix together in subsequent generations, but they are sometimes masked until they reappear distinctly again.

Sex-linked trait:

Sex-linked traits are caused by sex-linked genes. Sex-linked traits come from the x and y chromosomes or genes located on the sex chromosomes. Genes that are located only on the x chromosome. The female has two x chromosomes while the male has one x and one y chromosome.

Independent Assortment: - Second Law of Inheritance

States that during gamete formation, the segregation of each gene pair is independent of the others. The results are independent so one trait does not impact the result of the other. Two drait do not affect each other. Two different genes for example flower color and whether or not a gene is wrinkled do not affect each other. Takes place in meiosis I when the homologous chromosomes separate.

Recessive allele:

The allele that is only displayed when two recessive alleles are present. Reecessive alleles are represented by lowercase letters.

Probability

The chance that an outcome will occur. Determines the likelihood that an offspring will be born with certain characteristics. Probability = # of ways an event will occur/ # of possible outcomes. Probabilities are averages and not exact numbers.

Autosomes:

The first twenty two pairs of chromosomes in a body cells. Autosomes do not make a contribution on an organisms sex. The non-sex chromsomes. Follow autosomal inheritance patterns.

Based on what you know about Mendel's studies on purple and white flowers, why can genotype be different from phenotype?

The genotype is the genetic materials of an organism that can be identified as homozygous or heterozygous based on their pairs of alleles. Both alleles make up the genotype however one of the alleles is not being expressed or is masked. On the other hand, a phenotype is the name for the physical traits and characteristics displayed by an organism. While a plant may have alleles for both purple and white flowers, only the dominant allele will show.

Sex chromosome:

The last of the 23 pairs of chromosomes are the sex chromosomes. The xy chromosomes that contain specific genes, the x and y chromosomes do not share any corresponding genes. The y chromosome is much smaller than the x chromosome. Males only have one copy of the y chromosome so any recessive gene on a y chromosome will be expressed. Any recessive gene on an x chromosome will also be expressed in males because there is no second chromosome to mask the recessive allele's expression.The sex chromosomes develop the pattern for how an organism inherits traits.

During anaphase I of meiosis, copies of the same gene are separated as homologous chromosomes move to opposite sides of the cell. These chromosomes may or may not contain the same genetic information. Use evidence from meiosis to explain how gene separation occurs and why gametes only have one copy of each gene. How does the process of meiosis support the Law of Segregation?

The law of segregation is the separation of alleles when a gamete is being formed. During anaphase 1, homologous chromosomes are split and the daughter chromosomes only have half as much DNA as original cells, gametes only have one copy of each gene because in order to form an organism, a gamete must fuse together with another gamete and have a product of 46 chromosomes. That way the organism will have one copy of each gene from each parent. When the two gametes come together they create 46 chromosomes but if each had 46 chromosomes, then they would produce cells with 92 chromosomes which is too many. Further, in meiosis, diploid cells, which have two copies of chromosomes are split, each diploid has a pair of alleles but when homologous chromosomes are split, in Anaphase I of meiosis so are the pairs of alleles, that are located on the homologous chromosomes.

Locus:

The name for a specified location on homologous chromosomes. Comparable to an address, the locus identifies the part of the chromosome where the gene can be found. Gene location on a chromosome are the basis of heredity because they get passed down to offspring during reproduction.

Genotype:

The name for an organisms genetic makeup that can be referred to as either homozygous or heterozygous pairs of alleles. The allele combination is represented by a set of letters. Each body cell contains two alleles per gene, one from each parent in the homologous chromosome, two letter are therefore needed to represent each allele in the pair. Indicates which alleles the organism carries for a certain characteristic.

Allele:

The name for varying versions of a gene that can be found at a specific locus on a homologous chromosome. Human cells have one allele from each parent meaning that there are two alleles for each gene. All organisms that produce sexually including pea plants have alleles, two for each gene on the homolgous chrosomes of the body cells with one from each parent organism.

Homozygous:

The name for when there are two of the same alleles found at a specific locus on a homologous chromosome.

Genetic cross:

The name for when two organisms mate with each other. In genetic crossing, genetic material of both parent organisms are combined in the offspring.

Heterozygous:

The name for when two varying alleles can be found at the same locus on a homologous chromosome.

Phenotype:

The physical characteristics or traits that can be founds in an organism.

Law of segregation:

The process of separation between alleles that occurs when there is a gamete being formed. Each gamete has one allele instead of two. Gametes of a diploid organism only have onen gene because they are haploid. During meiosis, homologous chromosomes separate annd become gametes. The separation of chromosomes is additionally a separation of alleles. The gametes fuse during fertilization so the offspring has two companies of each genes, one of which from each parent. Separation of random chance of alleles from each parent. 50% chance of getting either allele from each parent.

Monohybrid:

The result when two parents with different variations of a traits mate together. Offspring which is a monohybrid shows many plants with one version of a trait and some plants with the alternate version.

Genetics:

The study of how an offspring inherits traits and characteristics from its parental organisms. Focusing on how traits are passed down and why they are unique from organism to organism.

Polygenic trait:

The term for characteristics in organisms that are influenced by more than one gene. Multiple genes play a role in polygenic traits. For example, over 600 genes affect height. Five different genes produce phenotype for mice fur color. Two genes for the color, one gene for the shade, another gene for whether the mouse has spots and the fifth gene that can overshadow all the others.

Dominant allele:

The term for the allele that is displayed when there are two dominant alleles present or when there are two different alleles present. However, the phenotype will remain the same as long is there is a dominant allele present in the genotype. Dominant alleles are represented by uppercase letters.

Codominance:

The term for when both of the alleles of a gene are expressed equally. That means that the phenotype will have an equal expression of both traits and characteristics derived from each allele. See the colors individually. Both traits are fully and separately expressed. For example, mixxinng a white feathered chicken with a black feathered chicken produces an offspring with equally visible both Black and white feathers.

Multiple Alleles:

The term for when there are a more than two alleles in a population. For example, blood type has three alleles. I^A, I^B, i. Both IA and IB are dominnant and have antigens. When together they are codominant and result in nAB blood. However, i is recessive and does not produce the protein known as an antigen. People with ii genotype do not have an antigen adn have type o-blood.

Trait:

Traits are distinguished characteristics in an organism that are inherited. Traits can vary from the parent to the offspring. Traits are not exact mixes of one generation from another because it can be observed that some generations go without being blended or having traits diluted. Offspring often look similar to their parents but not always.