7  •  Genes and Inheritance 277

Family resemblance: how traits are inherited

Why do offspring resemble their parents? 278

7.1

Family resemblance: your father and mother each contribute to your genetic makeup. 278

7.2

Some traits are controlled by a single gene. 280

7.3

Mendel learned about heredity by conducting experiments. 282

7.4

Segregation: you’ve got two copies of each gene but put only one copy in each sperm or egg. 284

7.5

Observing an individual’s phenotype is not sufficient for determining its genotype. 286

Probability and chance play central roles in genetics. 288

7.6

Chance is important in genetics. 288

7.7

A test-cross enables us to figure out which alleles an individual carries. 289

7.8

We use pedigrees to decipher and predict the inheritance patterns of genes. 291

How are genotypes translated into phenotypes? 293

7.9

Incomplete dominance and codominance: the effects of both alleles in a genotype can show up in the phenotype. 293

7.10

What’s your blood type? Some genes have more than two alleles. 295

7.11

Multigene traits: how are continuously varying traits such as height influenced by genes? 297

7.12

Sometimes one gene influences multiple traits. 298

7.13

Why are more men than women color-blind? Sex-linked traits differ in their patterns of expression in males and females. 299

7.14

This is how we do it: What is the cause of male-pattern baldness? 300

7.15

Environmental effects: identical twins are not identical. 302

Some genes are linked together. 304

7.16

Most traits are passed on as independent features: Mendel’s law of independent assortment. 304

7.17

Red hair and freckles: genes on the same chromosome are sometimes inherited together. 306

StreetBIO: KNOWLEDGE YOU CAN USE

Can a gene nudge us toward novelty-seeking (and spicy foods)? 308