Genetics Terminology Illustrated Epistasis A Presentation for The Angelfish Society May 20, 2007 by Tamar Stephens.

Slides:



Advertisements
Similar presentations
Genetics.
Advertisements

Inheritance. Inheritance Inheritance: the way genes are passed down. If a father doesn’t have a leg does that mean his children will be born with out.
1 Mendel’s Laws and Angelfish Genetics A presentation for The Angelfish Society February 21, 2010 By Tamar Stephens.
Punnet Square Notes.
Genetics Terminology Illustrated: Penetrance and Expressivity A Presentation for The Angelfish Society May 18, 2008 by Tamar Stephens.
Introduction to Angelfish Genetics
Genetics Terminology Illustrated: Genetic Crossover A Presentation for The Angelfish Society By Tamar Stephens For the October 19, 2008 TAS Meeting.
Heritability – “the fraction of the total variation in a trait that is due to variation in genes.” (Freeman and Herron, 2007) V p – the total variance.
TAS Angelfish Naming Conventions Part 2 – Phenotype Names A Presentation for The Angelfish Society by Tamar Stephens.
Mendelian Genetics Chapter 6 (6.3 – 6.5).
Genetics and Breeding. Interest Approach Ask students why they don’t look like each other (if they had the same parents)
Epistasis. Definition Epistasis is a form of gene interaction in which one gene masks the phenotypic expression of another. There are no new phenotypes.
Coat Color Genetics Coat color patterns are created by genes. Genes carry the genetic codes that create a horse’s size, conformation and color. Let’s.
1 Genetics Terminology Illustrated: Degrees of Dominance A Presentation for The Angelfish Society For the General Membership Meeting October 21, 2007 Prepared.
Equine Science Mr. Dieckhoff.  Heredity  Process of passing traits on to offspring  Genes  The basic unit of inheritance  A DNA sequence at a specific.
1 TAS Angelfish Naming Conventions Part 1 – Genetic Notation A Presentation for The Angelfish Society August 19, 2007 by Tamar Stephens.
Verifying and Documenting a New Mutation A presentation for The Angelfish Society August 16, 2009 Meeting By Tamar Stephens.
Dihybrid (or greater) Crosses: Review For either genotype or phenotype, the expected outcomes of a particular cross can be calculated by multiplying the.
KEY CONCEPT Phenotype is affected by many different factors.
Who was Mendel? Mendel – first to gather evidence of patterns by which parents transmit genes to offspring.
Lecture #2 Applying Mendel’s Principles Unit: Mendelian Genetics.
Observing Patterns in Inherited Traits Chapter 7.
BIOLOGY 12 Introduction to Genetics. “If our strands of DNA were stretched out in a line, the 46 chromosomes making up the human genome would extend more.
Genetics.
Theoretical genetics Learning objectives Success criteria Understand the basics of theoretical genetics Describe the interactions between loci (epistasis).
1 Black Angelfish – A Versatile Addition to a Breeding Program A presentation for The Angelfish Society February 17, By Tamar Stephens.
Genetics Michelle Bohanan March 27, © Gil Repetto.
Epistasis.
GENETICS PUNNETT SQUARES Tt T t T t. TOOLS TO KNOW A PUNNET SQUARE IS A TOOL USED TO PREDICT THE POSSIBLE GENOTYPES FOR THE OFFSPRING OF TWO KNOWN PARENTS.
Unit 4-.  The different forms of a gene  An allele whose trait always shows up in the organism when the allele is present.
Figure 12.5 Meiosis Accounts for the Segregation of Alleles (Part 1)
Gene interactions. A single character can be governed by two or more genes. They are called non - allelic or intergenic genetic interactions. The independent.
Write in composition book
Lecture #2 Applying Mendel’s Principles Unit: Mendelian Genetics
Notes-Genetics 1. Genetics is the study of how hereditary traits are passed between generations.
Epistasis.
How to do Test Crosses in Angelfish
Epistasis.
Review - A Gene is a piece of DNA that carries instructions for making a trait. It is passed from parent to offspring. This is called heredity. These chickens.
Combinations of Two Gene Pairs Involving Two Modes of Inheritance Modify the 9:3:3:1 Ratio
Patterns of Inheritance and Punnett Squares
EPISTASIS AND SEX LINKED
KEY CONCEPT Phenotype is affected by many different factors.
Patterns of inheritance
Gene Interactions Chapter 6, Part b
Intro to Genetics.
Genetics Definitions Definition Key Word
Genetics Vocabulary You will be using this vocabulary to complete the “project board assignment”
Phenotype the set of observable characteristics of an individual resulting from their DNA information.
KEY CONCEPT Phenotype is affected by many different factors.
Unit 5 “Mendelian Genetics”
KEY CONCEPT Phenotype is affected by many different factors.
Unit 5 “Mendelian Genetics”
Organization Every living thing has a set of characteristics inherited from its parent or parents. This is called heredity. Genetics is the study.
Genetics Punnett Squares.
KEY CONCEPT Phenotype is affected by many different factors.
Genetics definitions Label each chromosome pair as homozygous dominant, homozygous recessive, or heterozygous with definitions Label dominant.
Submission for new gene Suggested gene name – Philippine Blue Suggested gene designation – pb/pb and +/pb New Loci - yes Gene type is recessive.
Genetics Terminology Illustrated: Degrees of Dominance
KEY CONCEPT Phenotype is affected by many different factors.
How to Breed for Some Popular Varieties of Angelfish
Genetics Vocabulary Gene – a location on DNA that codes for a trait; located on both sets of chromosomes Allele – the specific gene that comes either from.
Section 6.4 “Traits & Genes”.
Intro to Genetics.
KEY CONCEPT Phenotype is affected by many different factors.
KEY CONCEPT Phenotype is affected by many different factors.
Carrier = an organism that has inherited a genetic trait or mutation, but displays no symptoms X-linked traits = traits that are passed on from parents.
KEY CONCEPT Phenotype is affected by many different factors.
KEY CONCEPT Phenotype is affected by many different factors.
KEY CONCEPT Phenotype is affected by many different factors.
Presentation transcript:

Genetics Terminology Illustrated Epistasis A Presentation for The Angelfish Society May 20, 2007 by Tamar Stephens

Have you ever seen… A smokey gold?A smokey gold? Or a zebra gold?Or a zebra gold? Or a half-black gold angelfish?Or a half-black gold angelfish? Well, why not?

That’s because of something called “epistasis” So what is epistasis?So what is epistasis?

What is Epistasis? Epistasis come from the Greek –Epistasis come from the Greek – –“epi” means “upon” –“histani” means “to place” So it means to place upon or to stand upon.So it means to place upon or to stand upon.

Definition “A nonreciprocal interaction between two non- alternative forms of genes in which one gene suppresses the expression of another affecting the same part of the organism” (American Heritage Dictionary) Wow! Is that crystal clear to you? Wow! Is that crystal clear to you?

Here’s a simpler definition “The situation in which the alleles at one gene cover up or alter the expression of alleles at another gene.” (Genetics, Weaver and Hedrick, Wm. C. Brown publishers,1989)

How is epistasis different from dominance? Dominance is when an allele suppresses the expression of another allele at the same locus. Pair of Chromosomes “A” Locus Aa “A” and “a” are alleles to each other. That means they are alternate forms of the gene at the “A” locus. If “A” suppresses the expression of “a” then “A” is dominant to “a.”

Epistasis involves two gene pairs Epistasis is when an allele at one locus masks (covers up) or alters the expression of an allele at a different locus. Pair of Chromosomes “A” Locus A “B” Locus B a B If the “A” allele at the A locus alters or masks the expression of the “B” allele at the B locus, then A is epistatic to B. (The B locus could be on the same chromosome as the A locus, or it could be on a different chromosome.)

Here is an example of dominance. The allele for black (D) and the allele for gold (g) are alternate forms of a gene at the same locus locus. If an angelfish has the genotype D/g, D is dominant and the angelfish will be black. Black+gold  black D/D+g/g  D/g

In fact, gold is recessive to all of the alleles at that locus Wild type: +/g = silverWild type: +/g = silver Dark: D/g = blackDark: D/g = black Marble: M/g = marbleMarble: M/g = marble Gold Marble:Gm/g = gold marbleGold Marble:Gm/g = gold marble Gold g/g = goldGold g/g = gold But in double dose (g/g) gold is epistatic to some alleles at other loci. Let’s look at a few.

Here is an example of epistasis Gold in double dose is epistatic to smokey.Gold in double dose is epistatic to smokey. Thus g/g – Sm/+ and g/g – Sm/Sm both look like a gold angelfish.Thus g/g – Sm/+ and g/g – Sm/Sm both look like a gold angelfish. The double dose of gold prevents the expression of the smokey trait.The double dose of gold prevents the expression of the smokey trait. This gold angelfish could have none, one, or two alleles for smokey. How would you find out?

To check for a hidden gene… Cross the gold angelfish with a wild type silver. (You need to know the genetics of the silver – it cannot have any hidden alleles! If must be wild-caught, or directly descended from wild-caught angels that have not been interbred with any domestics.) X What are the possible outcomes?

If the gold angelfish has no alleles for smokey… gg x +/+  100% (+/g) All of the offspring are silver angels, each with one recessive gold allele.

If the gold angelfish has one allele for smokey… Cross Gold x Silver g/g - Sm/+ x +/+ - +/+  50% of the offspring are +/g – Sm/+ smokey 50 % of the offspring are +/g - +/+

If the gold angelfish has two alleles for smokey… g/g – Sm/Sm x +/+ - +/+  100% +/g – Sm/+ smokey offspring

Can you think of another example where g/g is epistatic to another allele?Can you think of another example where g/g is epistatic to another allele?

Gold is epistatic to zebra! g/g – Z/+ = goldg/g – Z/+ = gold g/g – Z/Z = goldg/g – Z/Z = gold This zebra angelfish can have one allele for gold – but if it had two alleles (g/g), the gold would suppress the expression of zebra and it would be gold!

Have you ever seen a half-black gold? Gold (g/g) is epistatic to half-black (h/h). Thus: g/g - h/h = gold This half-black could have one hidden allele for gold. But if it had a double dose of gold, it would be gold!

So we have seen that g/g is epistatic to smokey, zebra, and half-black! Each one of these genotypes will be gold! g/g – Sm/+g/g – Sm/+ g/g – Sm/Smg/g – Sm/Sm g/g – Z/+g/g – Z/+ g/g – Z/Zg/g – Z/Z g/g – h/hg/g – h/h g/g – Sm/+ - Z/+g/g – Sm/+ - Z/+ Etc.Etc.

Is half-black epistatic to pearlscale? I read on a web site a few years ago that half-black was epistatic to pearl scale.I read on a web site a few years ago that half-black was epistatic to pearl scale. A few months ago, I asked on the TAFII forum if anyone had ever seen a half-black pearlscale, and….(next slide)A few months ago, I asked on the TAFII forum if anyone had ever seen a half-black pearlscale, and….(next slide)

Half-black pearlscale The next time I checked that thread, I found several photos of half-black pearlscale!The next time I checked that thread, I found several photos of half-black pearlscale! So is half-black epistatic to pearlscale? Obviously, the answer is no, because both traits are present and fully expressed.

Stripeless Stripeless is epistatic to the gene that codes for stripes in wild type angelfish.Stripeless is epistatic to the gene that codes for stripes in wild type angelfish. +/+ Wild type angelfish (silver with stripes) The addition of one stripeless allele modifies the expression of the wild type by suppressing expression of the stripes. +/+ - S/+ Silver ghost (no stripes)

That’s all Folks! The End