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BIOLOGY STANDARD 4
BIOLOGY STANDARD 4

... Allele - one form of a gene having two or more alternate forms, that occupy corresponding positions on homologous chromosomes Autosome - any chromosome other than the sex chromosome Carrier - an individual who is heterozygous for a recessive trait, and therefore will not express the trait, but may p ...
Notes Guide
Notes Guide

Genes and Alleles
Genes and Alleles

... Individual units called genes determine an organism’s traits. 2. A gene is a segment of DNA, located on the chromosomes, that carries hereditary instructions from parent to offspring. 3. For each gene, an organism typically receives one allele from each parent. ...
Objectives 8 - u.arizona.edu
Objectives 8 - u.arizona.edu

... heterogeneity is said to occur when the abnormal phenotype is caused by different mutations at the same locus, whereas locus (non-allelic) heterogeneity is used to describe a situation where a particular phenotype can be the result of mutations at two or more separate loci. 4) Interpret the type of ...
mandelian genetics - study
mandelian genetics - study

... A cross between a blue blahblah bird & a white blahblah bird produces offspring that are silver. The color of blahblah birds is determined by just two alleles. a) What are the genotypes of the parent blahblah birds in the original cross? b) What is/are the genotype(s) of the silver offspring? c) Wha ...
Chapter 3анаTest Review (KEY) 3.1 1
Chapter 3анаTest Review (KEY) 3.1 1

... 19. Heterozygous – What is it? and What does it look like? ­ having a  dominant AND a recessive allele (Bb)  20. Homozygous – What is it? and What does it look like? having 2  dominant (BB) or 2 recessive alleles (bb)  21. Incomplete dominance – when one trait is not completely dominant  over anoth ...
Mendel`s Genetics
Mendel`s Genetics

... from parents to offspring using the principles of probability 3. Geneticists use Punnett squares, charts that show all of the possible outcomes of a genetic cross. (See your worksheets on Mendel’s Work and Probability for examples. These will be on the test.) 4. A phenotype is an organism’s physical ...
Mendelian Genetics
Mendelian Genetics

... • Each organism contains two factors (alleles) for each trait. These factors segregate, or separate, in the formation of gametes (eggs and sperm). • This segregational behavior has a simple physical basis: the alignment of chromosomes are random on the metaphase plate during meiosis ...
Human Genetics: Dominant & Recessive Trait
Human Genetics: Dominant & Recessive Trait

... straight hair are examples of alleles for a trait that are codominant. Individuals with curly hair are homozygous for curly hair alleles. Individuals with straight hair are homozygous for straight hair alleles. Individuals who are heterozygous, with one of each allele have wavy hair, which is a blen ...
Chapter 3 Genetics Study Guide
Chapter 3 Genetics Study Guide

... Genes- factors that control a trait Trait- each different form of a characteristic: (hair color, eye color) Heredity-The passing on of physical characteristics from parents to offspring Genetics- the study of heredity Dominant- the trait that always shows up when this allele is present: represented ...
Week 29 Study Guide Define
Week 29 Study Guide Define

... Alleles- The different forms of a gene Gene- A segment of DNA on a chromosome that codes for a specific trait Dominant Alleles- An allele whos trait always shows up in the organism when the allele is present Recessive Alleles- An allele that is masked when a dominant allele is present Genotype- An o ...
How natural selection changes allele frequencies
How natural selection changes allele frequencies

... How natural selection changes allele frequencies Drift changes allele frequencies randomly (up or down) and slowly (proportional to 1/N). Selection biases the direction of allele-frequency change, and increases its speed. Alleles change frequency at speeds proportional to their difference in average ...
Section 14–1 Human Heredity
Section 14–1 Human Heredity

... certain human traits and disorders. It also describes how scientists study the inheritance of human traits. ...
Process of Evolution - Woodstown
Process of Evolution - Woodstown

... Bottleneck effect – natural disaster, reduce in population prevents the majority of genotypes from participating in the production of the next generation Founder effect – rare alleles occur at a higher frequency in a population isolated from a general ...
03 Non-mendelian Inheritance
03 Non-mendelian Inheritance

... 1. Give one genotype for a plant with 12 mm petals. 2. Give two possible genotypes for plants with 6 mm petals 3. What proportion of plants have 14 mm petals? 4. What is the phenotype of plants with 7 contributory alleles? 5. How many contributing alleles does a plant with 4mm petals have? ...
AIR Genetics Review PPT
AIR Genetics Review PPT

... In horses, black is dependent upon a dominant gene, B, and chestnut upon its recessive allele, b. The trotting gait is due to a dominant gene, T, the pacing gait to its recessive allele, t. If a heterozygous black pacer is mated to a chestnut trotter (heterozygous), what will be the appearance of t ...
Genetic engineering
Genetic engineering

... 1. Heterozygous round seeds Rr 2. Homozygous round seeds RR 3. Wrinkled seeds rr Give the phenotypes for the following genotypes: 4. RR Homozygous dominant 5. Rr Heterozygous 6. rr Homozygous recessive ...
PATTERNS OF INHERITANCE Gene - sequence of DNA that codes
PATTERNS OF INHERITANCE Gene - sequence of DNA that codes

... Incomplete Dominance Phenotype is intermediate between two parents. E.g., you cross a red-flowered snapdragon with a white one, and you get pink-flowered offspring. Has to do with the amount of red pigment required to make a red flower. If you have both alleles coding for pigment-producing proteins, ...
Gregor Mendel, 1822-1884
Gregor Mendel, 1822-1884

... 2. They reflect mechanisms through which specific alleles are expressed in the phenotype (i.e. this is not one allele subduing another at the DNA level) 3. They’re not related to the abundance of an allele within a population! ...
Practice Test - RHS AP Biology
Practice Test - RHS AP Biology

... 4. Several human inheritable diseases are caused by mutation and then passed on to subsequent generations. Anyone who inherits the mutation is destined to suffer from the disease and then has a 50% chance of passing it on to their children. Which of the following is an ethical question posed about t ...
Genetics: A Monk a Pea and a Fly
Genetics: A Monk a Pea and a Fly

... Other Types of Inheritance • Not all genes are dominant or recessive • Sometimes get both alleles, a modified form or the dominant or something new ...
` Mendelian Genetics 
` Mendelian Genetics 

... Genotype _________ phenotype  If T = tall and t = short, then   TT is a _________ plant  ...
Chapter 10 Patterns of Inheritance
Chapter 10 Patterns of Inheritance

... • The final phenotype may depend on the additive effects of several genes. ...
Ch 11 Reviewing this Chapter answers
Ch 11 Reviewing this Chapter answers

... shows only the dominant traits, but all possible phenotypes appear among the F2 generation. The 9:3:3:1 ratio allowed Mendel to deduce that factors segregate into gametes independently of other ...
Chapter 14 Mendel and the Gene Idea
Chapter 14 Mendel and the Gene Idea

... TECHNIQUE In a testcross, the individual with the unknown genotype is crossed with a homozygous individual expressing the recessive trait (white flowers in this example). By observing the phenotypes of the offspring resulting from this cross, we can deduce the genotype of the purple-flowered ...
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Dominance (genetics)



Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus. The first allele is dominant and the second allele is recessive. For genes on an autosome (any chromosome other than a sex chromosome), the alleles and their associated traits are autosomal dominant or autosomal recessive. Dominance is a key concept in Mendelian inheritance and classical genetics. Often the dominant allele codes for a functional protein whereas the recessive allele does not.A classic example of dominance is the inheritance of seed shape, for example a pea shape in peas. Peas may be round, associated with allele R or wrinkled, associated with allele r. In this case, three combinations of alleles (genotypes) are possible: RR, Rr, and rr. The RR individuals have round peas and the rr individuals have wrinkled peas. In Rr individuals the R allele masks the presence of the r allele, so these individuals also have round peas. Thus, allele R is dominant to allele r, and allele r is recessive to allele R. This use of upper case letters for dominant alleles and lower caseones for recessive alleles is a widely followed convention.More generally, where a gene exists in two allelic versions (designated A and a), three combinations of alleles are possible: AA, Aa, and aa. If AA and aa individuals (homozygotes) show different forms of some trait (phenotypes), and Aa individuals (heterozygotes) show the same phenotype as AA individuals, then allele A is said to dominate or be dominant to or show dominance to allele a, and a is said to be recessive to A.Dominance is not inherent to an allele. It is a relationship between alleles; one allele can be dominant over a second allele, recessive to a third allele, and codominant to a fourth. Also, an allele may be dominant for a particular aspect of phenotype but not for other aspects influenced by the same gene. Dominance differs from epistasis, a relationship in which an allele of one gene affects the expression of another allele at a different gene.
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