Summary
Summary DNA & Evolution
- Course
- Institution
here is a homemade summary of DNA and Evolution. I've completed this course with a 7.3. Hopefully you too!
[Show more]
Seller
Follownathalieridderhof
Content preview
DNA en Evolutie13.1 – Offspring acquire genes from parents by inheriting
chromosomes
Inheritance of genes
• Genes: A discrete unit of hereditary information consisting of a specific nucleotide
sequence in DNA.
- Program specific traits that emerge as we develop from fertilized eggs into adults.
• Most genes program cells to synthesize specific enzymes and other proteins, whose
cumulative action produces an organism’s inherited traits.
• Gametes; reproductive cells that transmit genes from one generation to the next.
• During fertilization, male and female gametes (sperm and eggs) unite, passing on
genes of both parents to their offspring.
• 46 chromosomes in their somatic cells.
• Locus; A specific place along the length of a chromosome where a given gene is
located.
• Genome; consists of the genes and other DNA that make up the chromosomes we
inherited from our parents.
Comparison of Asexual and sexual reproduction.
• In Asexual reproduction a single individual is the sole parent and passes copies of all
its genes to its offspring without the fusion of gametes.
- The genomes of the offspring are exact copies of the parent’s genome.
• Clone; A group of genetically identical individuals.
• Sexual reproduction: Two parents give rise to offspring that have unique
combinations of genes inherited from the two parents.
- Offspring vary genetically from their siblings and both parents.
13.2-fertilazation and meiosis alternate in sexual life cycles
Life cycle:
The generation-to-generation sequence of stages in the reproductive history of an organism
from conception to production of its own offspring.
Sets of chromosomes in Human cells
• Each somatic cell has 46 chromosomes.
• During Mitosis, chromosomes are condensed → can be distinguished from one
another.
• Two chromosomes of each 23 types.
, • Karyotype; A display of the chromosome pairs of a cell arranged by size and shape.
• Homologous chromosomes; two chromosomes of a pair have the same length,
centromere position and staining pattern.
• Both chromosomes of each pair carry genes controlling the same inherited
characters.
• Human females → homologous pair of X chromosomes (XX)
• Males → X chromosome and Y chromosome (XY)
- Sex chromosomes
• Others → autosomes
• We inherit one chromosome of a pair from each parent.
- A maternal set from our mother and a paternal set from our father.
• Diploid cell; Any cell with two chromosome sets.
- 2n (2n = 46)
• When chromosomes are duplicated → still diploid (2n)
• Haploid cells; Gametes which contain a single set of chromosomes.
- n (n = 23)
- 22 autosomes plus single sex chromosome.
Behavior of chromosomes sets in the human life cycle
• Human life begins with a haploid sperm from the father and a haploid egg from the
mother.
• Fertilization; The union gametes, culminating in fusion of their nuclei.
- Zygote; fertilized egg → diploid.
• Mitosis of the zygote and its descendant cells generates all the somatic cells in the
body.
- Chromosomes sets + genes are passes with precision to the somatic cells.
- Gametes are not produced by mitosis.
• Gametes develop from specialized cells (germ cells) in the gonads; ovaries in females
and testes in males.
• Meiosis; type of cell division that reduces the number of sets of chromosomes from
two to one in gametes, counterbalancing the doubling that occurs at fertilization.
- Each human sperm and egg is haploid (n = 23)
, - Fertilization restores the diploid condition by combining two sets of
chromosomes and the human life cycle is repeated, generation after generation.
• Fertilization and meiosis alternate in sexual life cycles, maintaining a constant
number of chromosomes in each species from one generation to the next.
The variety of sexual life cycles
• Gametes are the only haploid cells.
• Meiosis occurs in germ cells during the production of gametes, which undergo no
further cell division prior to fertilization.
- After fertilization, the diploid zygote divides by mitosis, producing a multicellular
organism that is diploid.
• Alternation of generations; second life cycle of plants and some species of algae.
- Sporophyte; the multicellular diploid stage.
*Meiosis produces haploid cells → spores
*spores doesn’t fuse with another cell
*divides mitotically
- Gametophyte; multicellular haploid stage.
* Cells give rise to gametes by mitosis
* Fusion of 2 haploid gametes at fertilization results in a diploid zygote.
- The sporophyte generation produces a gametophyte as its offspring
- The gametophyte generation produces the next sporophyte generation.
• Third life cycle → in most fungi and protists.
- After gametes fuse and form a diploid zygote, meiosis occurs without a
multicellular diploid offspring developing.
- Meiosis produces not gametes but haploid cells that then divide by mitosis and
give rise to either unicellular descendants (nakomelingen) or a haploid
multicellular adult organism.
- Haploid organism carries out further mitoses, producing the cells that develop
into gametes.
- Diploid stage → single-cell zygote
• Either haploid and diploid cells can divide by mitosis depending on the life cycle.
, 13.3 – Meiosis reduces the number of chromosomes sets from diploid
to haploid
Meiosis: Preceded by the duplication of chromosomes.
- Meioisis I
- Meioisis II
The two chromosomes of a homologous pair are individual chromosomes that were
inherited from each parent.
o Homologs may have different versions of genes at corresponding loci.
o Each version is called an allele of that gene.
Meiosis I
Prophase I:
o Spindle formation, nuclear envelope breakdown.
o Chromosomes condense
o Crossing over; The reciprocal (onderling) exchange of genetic material between
nonsister chroma-tids
- Chiasmata; X-shaped regions where crossovers have occurred.
o Microtubules from one pole or the other attach to the kinetochores, one at the
centromere of each homolog.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller nathalieridderhof. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $7.97. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
68443 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 15 years now