Unit 3 Sexual reproduction and genetics: Chapter 11, 12, 13, 14 and 15

Meiosis

Creates haploid daughter cells

Sexual reproduction

Alternation of haploid gametes with diploid zygotes

Germ-line cells

in multicellular organism’s, cells whose descendants may eventually form gametes are

Synapsis

Early in meiosis, chromosomes pair up in a process called

synaptonemal complex

The chromosomes are held together by a complex of proteins called the

Crossing over, Genetic recombination

During synapsis, homologous sections of DNA may exchange places, This is called_____and result in____

Independent assortment

the orientation of homologous chromosomes

Dominant traits

Are always expressed when inherited

An individual homozygous dominant for trait A (genotype AA) mates with one homozygous recessive for the same trait (genotype aa) what genotype and phenotype will their offspring have?

They will all be heterozygous with a dominant phenotype

The Principle of Segregation says that

Gametes inherit only a single allele of each gene

According to the principle of independent assortment

A gamete may inherit any combination of maternal and paternal alleles

Continuous traits

Are likely to be polygenic

You mate two plants together and plant some of the resulting seeds in a greenhouse and some in an outdoor garden. Those planted in the garden are shorter on average than those in the greenhouse. What is the likely explanation?

Phenotypic plasticity

Multiple alleles of a gene code for alternate functional versions of an enzyme. What pattern of inheritance would be most likely for these traits?

Codominace

You examine a mammal where a single gene H codes for hair patterns. HH individuals have long hair, hh individuals are bald, and Hh individuals have short hair. What pattern of inheritance have you observed?

Incomplete dominance

The chromosomal theory of inheritance states that

The inheritance of traits is mediated by the inheritance of chromosomes

Autosomes are

Chromosomes not involved in sex determination

Sex linked traits

May be expressed more often in certain sexes than others

Where would you most likely encounter dosage compensation?

In a homozygous individual of a species with an XY sex determination system

Recessive traits

May skip generations in pedigree analysis

What is the relationship between dominance and sex-linkage of a trait

There is no relationship dominance is determined by whether a gene codes for a functional protein and sex-linkage is whether a gene occurs on a sex chromosome

The complementarity of the two strands of a DNA molecule mean that

You can determine the nucleotide sequence on one strand if you know the sequence on the other

During DNA replication

Each strand of the original molecule is used as a template for a new strand

During DNA replication, primers

Are made of RNA by RNA polymerase

Where would you find Okazaki fragments?

The lagging strand of a replication fork

What is the difference between the leading and lagging strand of a replication fork?

The leading strand can be replicated in one continuous segment, while the lagging strand is copied in multiple segments

What is the difference between DNA polymerase 1 and DNA polymerase 3

DNA polymerase 1 replaces RNA primers with DNA, while DNA polymerase 3 synthesizes new DNA strands

What does telomerase do?

Extends telomeres

Mutagens

Cause changes in DNA structure or sequence

In DNA transcription

A segment of DNA is copied into a strand of mRNA

The genetic code

May contain multiple codons that code for more than one amino acid

Silent mutations

Are possible because the genetic code is degenerate

Transfer RNA (tRNAs)

Form the link between nucleotide codons and amino acids

Mutations

Is/are the ultimate source of all genetic variation

All of the following are common modifications of eukaryotes RNA transcripts expect

Transcription by DNA polymerase instead of RNA polymerase

Promoter sequences

Serve as binding sites for RNA polymerase

Eukaryotes may produce multiple proteins products from a single gene through the use of

Alternate splicing of exons

The genetic code includes two types of punctuation codons called____codons and ____ codons

Start, stop