What does this Genetics cheat sheet cover?

It has 10 sections: Mendelian laws, Punnett ratios, Dihybrid crosses, Non-Mendelian, Sex-linked, Pedigrees, Linkage, Hardy-Weinberg, Mutation and Chi-square. Together they cover the topics a typical Genetics exam tests, including Mendel's laws, Punnett squares and ratios, dihybrid crosses and incomplete dominance, codominance, epistasis.

Is the genetics cheat sheet free?

The first part is free to read on this page, with no account needed. The full sheet opens in the app with Unlimited ($4.99 a month or $19 for a semester), where you can edit it, print it or save it as a PDF. It is one US Letter page and prints cleanly in black and white or colour.

Can I bring this Genetics cheat sheet to my exam?

Only if your course allows a note sheet, so check the syllabus. This one is a single US Letter page. If your exam allows a different size, such as a 3x5 or 4x6 index card or one page front and back, Cheat Sheet AI makes one at exactly that size from your own lecture notes.

The sheet was written by our engine from a standard course outline, then a second model fact-checked every formula and statement against it; it corrected 2 statements before publishing. Notation and emphasis vary between courses, so check it against your own lecture notes.

Can I make a Genetics sheet from my own notes?

Yes. Upload your lecture slides, notes or study guide and Cheat Sheet AI writes a sheet in your course's notation, sized to exactly the space your exam allows. Your first sheets are free.

Chemistry & BioGenetics

Genetics Cheat Sheet — 1-page PDF

Mendelian inheritance, linkage, Hardy-Weinberg, mutation, chi-square. The whole course on one dense, printable page for your midterm or final, with every formula typeset and worked examples where they help.

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For a specific exam: Genetics Final exam study sheet.

1 pageUS Letter
10 sections10 topics
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Preview of the one-page Genetics cheat sheet: Mendelian inheritance, linkage, Hardy-Weinberg, mutation, chi-square — the whole course, one page

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What’s on it

The topics a typical Genetics exam tests, all on the one page.

Mendel's laws
Punnett squares and ratios
Dihybrid crosses
Incomplete dominance, codominance, epistasis
Sex-linked inheritance
Pedigree analysis
Linkage and recombination frequency
Hardy-Weinberg equilibrium
Mutations
Chi-square for genetics

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The free part of the sheet, section by section. Unlock the full sheet to read the rest, edit any block, and print it or save it as a PDF.

01Mendelian laws

Gene / allele: Gene: hereditary unit at a locus. Alleles: alternative forms of a gene.
Genotype / phenotype: Genotype: allele combination. Phenotype: observable trait.
Homozygous / heterozygous: Homozygous: same alleles ( $AA$ or $aa$ ). Heterozygous: different alleles ( $A a$ ).
Dominant / recessive: Dominant allele expressed in heterozygote; recessive expressed only when homozygous.

Segregation

allele pairs segregate during gamete formation; each gamete receives one allele

Mendel's 1st law

Independent assortment

alleles of different genes assort independently if genes are unlinked

Mendel's 2nd law; valid when loci on different chromosomes or far apart

Test cross: Cross with homozygous recessive individual to reveal unknown genotype.

Monohybrid $A a \times A a$

Genotypes $1 AA : 2 A a : 1 aa$ ; phenotypes $3$ dominant: $1$ recessive (complete dominance).

02Dihybrid crosses

Dihybrid count $AaBb \times AaBb$ : probability of $aabb$ ?

$(1/4) (1/4) = 1/16$ .

Watch out:If loci are linked, $9 : 3 : 3 : 1$ often fails; use recombination frequency instead.

03Non-Mendelian

Incomplete dominance: Heterozygote phenotype is intermediate between homozygotes.

Incomplete dominance ratio

A a \times A a \to 1 : 2 : 1

phenotype ratio equals genotype ratio

Codominance: Both alleles fully expressed in heterozygote.

ABOWhy is $I^{A} I^{B}$ codominant?

Both $A$ and $B$ antigens are expressed in the heterozygote.

Epistasis: One gene masks or modifies expression of another gene at a different locus.

Classic epistasis ratios

Type	Phenotypic ratio	Key idea
Recessive epistasis	$9 : 3 : 4$	homozygous recessive masks other locus
Dominant epistasis	$12 : 3 : 1$	dominant allele masks other locus
Complementary genes	$9 : 7$	both dominant alleles required
Duplicate dominant	$15 : 1$	either dominant allele gives trait

04Sex-linked

X-linked cross $X^{A} X^{a} \times X^{A} Y$

Daughters: $1/2$ normal, $1/2$ carriers. Sons: $1/2$ normal, $1/2$ affected.

05Pedigrees

Pedigree: Family diagram tracking a trait across generations.

Pattern clues

Pattern	Suggests
Every generation	dominant
Skipped generations	recessive
More males	X-linked recessive
Father-to-son present	autosomal or Y-linked; not X-linked
Affected father -> all daughters	X-linked dominant
Affected mother -> all sons?	check cytoplasmic or X-linked rules

Autosomal dominant: Affected individuals usually have an affected parent; male-to-male transmission possible.
Autosomal recessive: Affected offspring can arise from unaffected carrier parents; may skip generations.
Y-linked: Only males affected; father to all sons.

06Hardy-Weinberg

Allele counts

p = \frac{2 N _{AA} + N _{A a}}{2 N}, q = \frac{2 N _{aa} + N _{A a}}{2 N}

from observed genotype counts

H-W exampleIf $q^{2} = 0.04$ , find $q, p, 2 pq$ .

$q = 0.2$ , $p = 0.8$ , heterozygotes $2 pq = 0.32$ .

Watch out:Use observed counts to estimate $p, q$ only before testing H-W; expected counts come from $p^{2}, 2 pq, q^{2}$ .

07Mutation

Mutation: Permanent change in DNA sequence.

Mutation types

Type	Effect
Substitution	one base replaced
Insertion / deletion	frameshift if not in multiples of $3$
Nonsense	creates stop codon
Missense	amino acid change
Silent	same amino acid
Duplication / inversion / translocation	chromosomal rearrangements

Germline vs somatic: Germline mutations are heritable; somatic mutations affect the individual, not offspring.

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Also on the full Genetics sheet

9 more sections, with every definition, formula and worked example. Unlimited unlocks every full sheet in the library to edit, print or save as a PDF, and makes unlimited sheets from your own notes.

Punnett ratios

Product rule
Binomial gametes
Common Mendelian ratios
Backcross

Dihybrid crosses

9:3:3:1
Two-factor test cross
Gamete types
Probability of a phenotype combo

Non-Mendelian

Sex-linked

Sex-linked gene
Hemizygous
X-linked recessive pattern
Transmission rules
X-inactivation

Pedigrees

Linkage

Linked genes
Recombinants
Recombination frequency
Map unit
Linkage interpretation

Hardy-Weinberg

H-W
H-W genotype
Equilibrium conditions

Mutation

Spontaneous / induced

Chi-square

Chi-square
Degrees of freedom
Null hypothesis
Decision rule

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FAQ

Questions

About the Genetics sheet and making your own.

What does this Genetics cheat sheet cover?: It has 10 sections: Mendelian laws, Punnett ratios, Dihybrid crosses, Non-Mendelian, Sex-linked, Pedigrees, Linkage, Hardy-Weinberg, Mutation and Chi-square. Together they cover the topics a typical Genetics exam tests, including Mendel's laws, Punnett squares and ratios, dihybrid crosses and incomplete dominance, codominance, epistasis.
Is the genetics cheat sheet free?: The first part is free to read on this page, with no account needed. The full sheet opens in the app with Unlimited ($4.99 a month or $19 for a semester), where you can edit it, print it or save it as a PDF. It is one US Letter page and prints cleanly in black and white or colour.
Can I bring this Genetics cheat sheet to my exam?: Only if your course allows a note sheet, so check the syllabus. This one is a single US Letter page. If your exam allows a different size, such as a 3x5 or 4x6 index card or one page front and back, Cheat Sheet AI makes one at exactly that size from your own lecture notes.
How accurate is it?: The sheet was written by our engine from a standard course outline, then a second model fact-checked every formula and statement against it; it corrected 2 statements before publishing. Notation and emphasis vary between courses, so check it against your own lecture notes.
Can I make a Genetics sheet from my own notes?: Yes. Upload your lecture slides, notes or study guide and Cheat Sheet AI writes a sheet in your course's notation, sized to exactly the space your exam allows. Your first sheets are free.

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